WEBVTT 1 00:00:01.040 --> 00:00:05.320 Section fourteen of the Science History of the Universe, Volume four. 2 00:00:05.919 --> 00:00:09.880 This is a LibriVox recording. All LibriVox recordings are in 3 00:00:09.919 --> 00:00:14.119 the public domain. For more information or to volunteer, please 4 00:00:14.199 --> 00:00:17.760 visit LibriVox dot org. This is a recording by joe 5 00:00:17.760 --> 00:00:22.000 Anne Crosby the Science History of the Universe, Volume four, 6 00:00:22.719 --> 00:00:27.640 edited by Francis Rolt Wheeler. Chemistry, Chapter ten, The Atomic 7 00:00:27.760 --> 00:00:31.440 Theory and the work of Davy. A desire injinite in 8 00:00:31.480 --> 00:00:34.640 the human mind to find an explanation of natural phenomena 9 00:00:35.280 --> 00:00:39.359 by the aid of speculations respecting the ultimate constituents of 10 00:00:39.439 --> 00:00:45.600 matter resulted in guesses and ideas concerning Adams in olden times, without, however, 11 00:00:45.679 --> 00:00:50.280 the evolution of an exact chemical atomic theory. With respect 12 00:00:50.280 --> 00:00:54.479 to the hypothesis of the ancient philosophers regarding the constitution 13 00:00:54.640 --> 00:00:58.520 of matter, the following estimate by Clifford will suffice in 14 00:00:58.600 --> 00:01:02.200 this connection. From the earliest times that man began to 15 00:01:02.240 --> 00:01:05.640 form any coherent idea in the world at all, they 16 00:01:05.680 --> 00:01:08.519 began to guess, in some way or other, how it 17 00:01:08.719 --> 00:01:10.640 was that it all began, and how it was all 18 00:01:10.680 --> 00:01:14.239 going to end. Modern speculations are attempts to find out 19 00:01:14.280 --> 00:01:17.480 how things began and how they are to end, by 20 00:01:17.519 --> 00:01:20.640 consideration of the way in which they are going on. Now, 21 00:01:22.159 --> 00:01:24.200 a great number of people appeared to have been led 22 00:01:24.200 --> 00:01:27.280 to the conclusion that the modern theory of the molecular 23 00:01:27.359 --> 00:01:31.840 constitution of matter was very similar to the guesses which 24 00:01:31.879 --> 00:01:36.000 we find in ancient writings Democratus and Lucratus. It so 25 00:01:36.079 --> 00:01:38.560 happens that these ancient writers did hold a view of 26 00:01:38.640 --> 00:01:42.280 the constitution of things which in many striking respects agrees 27 00:01:42.319 --> 00:01:45.239 with the view which we hold in modern times. The 28 00:01:45.239 --> 00:01:48.480 difference between the ancient and modern views is mainly this. 29 00:01:49.480 --> 00:01:52.200 The atomic theory of Democratus was a guess, and no 30 00:01:52.280 --> 00:01:55.560 more than a guess. Everybody around him was guessing about 31 00:01:55.599 --> 00:01:58.079 the origin of things, and they guess in a great 32 00:01:58.159 --> 00:02:01.359 number of ways to make a guess which was more 33 00:02:01.439 --> 00:02:04.480 near the right thing than any of the others end. 34 00:02:05.120 --> 00:02:08.159 The conception of Adams had up to the close of 35 00:02:08.199 --> 00:02:11.479 the eighteenth century been almost entirely the property of the 36 00:02:11.520 --> 00:02:17.159 metaphysician and the mathematical physicist, and had assisted in extending 37 00:02:17.199 --> 00:02:21.479 their sciences. With the exception of Serenate and Boyle, chemists 38 00:02:21.479 --> 00:02:25.000 had aided little in its formation, and less in its establishment, 39 00:02:25.439 --> 00:02:28.080 nor had they derived inspiration from it for the proper 40 00:02:28.120 --> 00:02:31.199 founding of their own science. For more than a century 41 00:02:31.240 --> 00:02:34.400 they had been following the igneous fatuus of a false 42 00:02:34.439 --> 00:02:39.879 theory of combustion and a most elusive hypothetical Phlogiston. The 43 00:02:39.919 --> 00:02:42.639 close of the eighteenth century found them engaged in a 44 00:02:42.639 --> 00:02:46.120 bitter strife over these theories, and who fully occupied to 45 00:02:46.120 --> 00:02:48.599 think of much else than the destruction of the old 46 00:02:48.599 --> 00:02:52.520 beliefs and the adaptation of the new. The mastermind of Levoisier, 47 00:02:52.960 --> 00:02:56.240 who had brought this revolution, was busied with the greater 48 00:02:56.319 --> 00:03:00.000 work of reconstruction, and dealing a little with the hypothesis, 49 00:03:00.199 --> 00:03:03.840 which could not be directly proved by experiments in his laboratory, 50 00:03:04.560 --> 00:03:09.360 was laying broad and strong foundations of the new chemistry. Consequently, 51 00:03:09.360 --> 00:03:14.120 the works of Bergmann, Shiel, Priestley, Black, Cavendish, Macker, and 52 00:03:14.199 --> 00:03:17.400 others did not treat of atoms in their moving forces, 53 00:03:17.759 --> 00:03:21.159 except in an occasional indefinite reference to some sort of particle. 54 00:03:21.479 --> 00:03:23.840 Yet the chemists were the very one required to undertake 55 00:03:23.840 --> 00:03:27.439 the scientific development of the atomic hypothesis and to establish 56 00:03:27.479 --> 00:03:30.439 it as a theory, by discovering a series of facts 57 00:03:30.759 --> 00:03:33.599 which were connected together by it, and found in it 58 00:03:33.800 --> 00:03:37.919 a simple explanation. In seventeen eighty three, the English chemist 59 00:03:38.039 --> 00:03:41.439 Kurwan went so far as to refer to affinity as 60 00:03:41.479 --> 00:03:45.919 the force which holds atoms so intimately together that simple 61 00:03:46.199 --> 00:03:50.599 mechanical means are insufficient to separate them, while as Countryman Higgins, 62 00:03:50.719 --> 00:03:55.000 writing in seventeen ninety on the composition of sulfurous in 63 00:03:55.319 --> 00:03:59.240 sulfuric acid, expresses the opinion that the atom of sulfur 64 00:03:59.639 --> 00:04:02.319 is with one atom of oxygen in the first but 65 00:04:02.360 --> 00:04:05.639 with two atoms in the second. It is in the 66 00:04:05.719 --> 00:04:08.759 view of this statement and others similar to it, that 67 00:04:08.800 --> 00:04:11.800 some have regarded Higgins as the real originator of the 68 00:04:11.919 --> 00:04:16.680 modern atomic doctrine. However, Higgins restricted his attention to a 69 00:04:16.720 --> 00:04:20.399 small number of compounds. His conceptions were not consistent with 70 00:04:20.480 --> 00:04:24.399 the fact he regarded those weights of elements which combine 71 00:04:24.600 --> 00:04:27.680 to form the simplest compounds as in general equal, and 72 00:04:27.759 --> 00:04:30.519 he made no attempt to seek confirmation for any theory 73 00:04:30.600 --> 00:04:33.560 he had in the laboratory. For long, the common consent 74 00:04:33.639 --> 00:04:36.839 of the public opinion was given the undivided honor due 75 00:04:36.839 --> 00:04:40.199 to the discoverer of the great atomic generalization in its 76 00:04:40.279 --> 00:04:44.199 modern aspect to John Dalton. Before the establishment of the 77 00:04:44.240 --> 00:04:48.519 chemical atomic theory could be brought to completion, however, it 78 00:04:48.560 --> 00:04:53.079 became necessary to fix the significance of the term chemical proportions, 79 00:04:53.600 --> 00:04:57.519 according to which simple substances unite to form compound bodies, 80 00:04:58.160 --> 00:05:00.800 and an important part of this question was solved by 81 00:05:00.839 --> 00:05:05.519 two chemists prior to Dalton, Richter and Proust. Jeremiah Benjamin 82 00:05:05.600 --> 00:05:10.800 Richter seventeen sixty two eighteen oh seven, published in his 83 00:05:11.519 --> 00:05:16.680 de Yusu mattheos in Shumia seventeen eighty nine, Alfans Grunde 84 00:05:17.000 --> 00:05:23.720 der stokem itri Uda meskunst Schimisha Stelemanta seventeen forty two 85 00:05:23.839 --> 00:05:30.600 seventeen ninety four and uberdainyrin gegenstande Dayershumi seventeen ninety one 86 00:05:31.199 --> 00:05:36.040 eighteen oh two. The results of researches made mainly Well 87 00:05:36.079 --> 00:05:39.959 employed as a works chemist in Berlin. The last two 88 00:05:40.040 --> 00:05:43.720 mentioned trustees contained the conclusion which he drew from his 89 00:05:43.839 --> 00:05:48.360 work upon the proportions by weight in various compounds. Richter 90 00:05:48.480 --> 00:05:52.399 looked upon chemistry as a branch of applied mathematics and 91 00:05:52.519 --> 00:05:56.040 exhibited all the distressing qualities of a person possessed by 92 00:05:56.040 --> 00:05:59.720 a fixed idea. He spent his life in seeking a 93 00:05:59.800 --> 00:06:04.560 rethmetical regularities and the weights of acids and alkalis, neutralizing 94 00:06:04.600 --> 00:06:09.120 each other, and finding them in spite of their non existence. Nevertheless, 95 00:06:09.160 --> 00:06:12.639 he managed to make discoveries of the highest importance. He 96 00:06:12.759 --> 00:06:16.319 not only noticed but also correctly interpreted the fact that 97 00:06:16.360 --> 00:06:20.040 when two neutral salts decompose one another, the resulting salts 98 00:06:20.040 --> 00:06:24.600 are neutral. To quote his conclusions concerning that very common 99 00:06:24.759 --> 00:06:30.160 experience that two neutral salts on decomposition again produce neutral compounds, 100 00:06:30.759 --> 00:06:34.480 I could draw no direct inference other than that fixed 101 00:06:34.560 --> 00:06:39.319 quantitative relations must exist between the constituents of the neutral salts. 102 00:06:40.240 --> 00:06:43.399 If a solution of two compounds is so constituted that 103 00:06:43.519 --> 00:06:47.000 neither of them, as long as it remains in the solution, 104 00:06:47.839 --> 00:06:52.839 exhibits the peculiar characteristics it had before solution example, given 105 00:06:53.680 --> 00:06:57.360 the reactions of an acid or of an alkali, then 106 00:06:57.399 --> 00:07:00.720 such a solution is called saturated or neutral, or also 107 00:07:00.759 --> 00:07:05.439 a neutral compound. When two neutral solutions are mixed and 108 00:07:05.439 --> 00:07:10.279 a decomposition ensues, the newly formed products are also, almost 109 00:07:10.279 --> 00:07:13.959 without exception neutral. Hence, it follows that if the combining 110 00:07:14.480 --> 00:07:18.040 ratios in the original compounds be known. Those in the 111 00:07:18.079 --> 00:07:22.600 newly formed compounds are also known end cf. Wenzel, seventeen 112 00:07:22.680 --> 00:07:26.920 forty seventeen ninety three. At an earlier date, seventeen seventy 113 00:07:26.959 --> 00:07:32.040 seven had demonstrated that acids and bases combine in constant proportions, 114 00:07:32.399 --> 00:07:35.560 but it failed to note the persistency of the neutrality 115 00:07:36.040 --> 00:07:41.120 in the double decomposition of the neutral salts. Richter deduced 116 00:07:41.120 --> 00:07:45.120 from the maintenance of neutrality when one metal precipitates another 117 00:07:45.199 --> 00:07:49.519 from a neutral solution, a relation Bergmann had observed, by 118 00:07:49.519 --> 00:07:53.360 which he interpreted in terms of another theory, that the 119 00:07:53.439 --> 00:07:56.480 quantities of two metals which dissolve in the same amount 120 00:07:56.480 --> 00:07:59.360 of acid also unite in their oxides with the same 121 00:07:59.360 --> 00:08:03.319 amount of oxen. Therefore, he established that quantities of two 122 00:08:03.319 --> 00:08:06.959 substances which were equivalent in one reaction are also equivalent 123 00:08:07.000 --> 00:08:10.959 in the others. He was the originator of stoiccheometry, or 124 00:08:11.040 --> 00:08:14.439 the art of chemical measurement, which had to deal with 125 00:08:14.480 --> 00:08:18.360 the laws according to which substances unite to form chemical compounds. 126 00:08:19.319 --> 00:08:23.920 Nonwithstanding the fact that Richter's trustees contained such important discoveries, 127 00:08:24.120 --> 00:08:27.720 these remained unrecognized until Fischer published a table of the 128 00:08:27.759 --> 00:08:31.560 relative affinities of bases and acids, founded on the values 129 00:08:31.639 --> 00:08:36.799 Richter had obtained in his translation of Bertola's Richersch made 130 00:08:36.799 --> 00:08:41.480 in eighteen o two. Bertoll accepted the law of proportionality 131 00:08:42.440 --> 00:08:45.159 and gave an account of it in his Assay de 132 00:08:45.279 --> 00:08:50.279 Statique Chemik, in which he reprinted Fisher's note. Thus, Richter's work, 133 00:08:50.480 --> 00:08:53.399 which at the time of its publication had been almost 134 00:08:53.480 --> 00:08:59.320 completely ignored, became more widely known and appreciated. Louis Jose 135 00:08:59.519 --> 00:09:04.600 Prauss seventeen fifty five eighteen twenty six, although a Frenchman 136 00:09:04.639 --> 00:09:08.679 by birth, conducted his most important researches in Madrid, where 137 00:09:08.679 --> 00:09:11.519 he settled after seventeen ninety one. The work for which 138 00:09:11.519 --> 00:09:13.840 he has celebrated was the result of a series of 139 00:09:13.919 --> 00:09:17.679 questions which Bertolai had advanced. The two works of Bertolas 140 00:09:17.759 --> 00:09:23.679 on affinity Richerche surlet luis de la finiti and Essay 141 00:09:23.840 --> 00:09:28.200 don Statique Chemique were particularly directed against false views of 142 00:09:28.240 --> 00:09:31.679 affinity and a misuse of the so called affinity tables 143 00:09:31.679 --> 00:09:35.200 of Geoffrey Bergman and others. He contended that affinity was 144 00:09:35.240 --> 00:09:38.600 by no means a simple force, an easy to determine 145 00:09:38.679 --> 00:09:43.399 or measure, but was influenced by temperature, physical state cohesion, 146 00:09:43.480 --> 00:09:47.320 and especially by mass, the latter largely determined the course 147 00:09:47.399 --> 00:09:50.840 of chemical reactions. He went further, however, and from the 148 00:09:50.919 --> 00:09:54.120 correct premises of the influence of mass on the chemical 149 00:09:54.600 --> 00:09:59.360 effort produced, Bertolas drew the erroneous inference that mass had 150 00:09:59.360 --> 00:10:02.559 an influence not only on the amount of change, but 151 00:10:02.720 --> 00:10:06.320 also on the kind, producing a continuous variation in the 152 00:10:06.440 --> 00:10:10.399 ratio in which the constituents are united in a compound. 153 00:10:10.879 --> 00:10:15.200 He asserted the variability of the composition of chemical compounds, 154 00:10:15.720 --> 00:10:19.840 the possibility of combination between constituents, and all sorts of 155 00:10:19.879 --> 00:10:24.799 continuously varying ratios. None of the other leading chemists of 156 00:10:24.840 --> 00:10:27.799 the day were able to concur with his views as 157 00:10:27.840 --> 00:10:31.080 to the lack of any fixity or constancy of proportion 158 00:10:31.600 --> 00:10:35.799 in chemical compounds. Yet they raised no objection, probably owing 159 00:10:35.840 --> 00:10:39.480 to Bertolai's reputation, and it remained for Pross to attack 160 00:10:39.519 --> 00:10:44.519 the theoretical conclusions of his eminent contemporary, Praus. Numerous papers 161 00:10:44.519 --> 00:10:48.480 in his controversy with Bertolai appeared in the journal Deficique 162 00:10:48.960 --> 00:10:51.840 between the years eighteen oh two and eighteen oh eight. 163 00:10:52.320 --> 00:10:55.840 The lucidity of the arguments employed, the variety of the 164 00:10:55.879 --> 00:10:59.279 experimental work described, and the freedom and keenness of the 165 00:10:59.320 --> 00:11:03.440 style entered. These papers, which deal exclusively with the distinctly 166 00:11:03.559 --> 00:11:08.480 dry subject of quantitative analysis most interesting reading even now. 167 00:11:08.639 --> 00:11:12.559 Prousse proves that substances formed under the most varied conditions 168 00:11:12.720 --> 00:11:16.200 have a fixed composition, and he shows that Bertille's examples 169 00:11:16.279 --> 00:11:20.919 of variable composition were all cases of mixtures. This involves 170 00:11:21.080 --> 00:11:24.679 him in the necessity of discriminating between mixtures and compounds, 171 00:11:25.200 --> 00:11:29.240 and undertaking the difficulties of which he fully realized and 172 00:11:29.360 --> 00:11:31.519 with which he dealt in a manner very much like 173 00:11:31.600 --> 00:11:35.240 that still resorted to for the same purpose von Meyer. 174 00:11:35.960 --> 00:11:39.440 In seventeen ninety nine. Prouss had proved the constant composition 175 00:11:39.519 --> 00:11:43.879 of native and artificial carbonate of copper, and had enunciated 176 00:11:43.919 --> 00:11:48.159 the general principle of which this constituted. An example of 177 00:11:48.240 --> 00:11:51.639 greater importance than these, where observations he made upon the 178 00:11:51.679 --> 00:11:55.320 two compounds iron forms with sulfur and the two stages 179 00:11:55.320 --> 00:11:59.600 of oxidation shown by tin. He father investigated the compounds 180 00:11:59.600 --> 00:12:04.120 of many cobalt, nickel, and copper, and throughout he found 181 00:12:04.240 --> 00:12:08.120 that vary the conditions and relative masses at pleasure. The 182 00:12:08.200 --> 00:12:12.440 oxides and sulfides produced always have a definite composition. To 183 00:12:12.519 --> 00:12:15.360 be sure, an element might combine with oxygen or sulfur 184 00:12:15.399 --> 00:12:19.320 in two proportions, but each has a compound of definite proportions. 185 00:12:19.720 --> 00:12:22.879 Prowse showed the air which underlay the old method of 186 00:12:22.960 --> 00:12:26.559 determining the quantity of oxygen and oxides, of estimating the 187 00:12:26.600 --> 00:12:30.399 metal and calculating the oxygen by difference, proving that in 188 00:12:30.440 --> 00:12:33.799 many cases the bodies so examined were not oxides at all, 189 00:12:33.960 --> 00:12:39.120 but compounds containing hydrogen hydrooxides we now call them. He 190 00:12:39.200 --> 00:12:42.559 moreover demonstrated that many of the bodies on analysis of 191 00:12:42.600 --> 00:12:47.519 which Bertolt had based his generalizations were not simple at all, 192 00:12:47.720 --> 00:12:52.360 but mixtures of substances themselves of perfectly definite composition. So 193 00:12:52.519 --> 00:12:57.399 accurate were his analytical investigations and zoological his reasoning that 194 00:12:57.480 --> 00:13:01.080 Bertolu was overcome at every point. The law of definite 195 00:13:01.159 --> 00:13:04.039 chemical proportions as we now have it, was the fruit 196 00:13:04.159 --> 00:13:07.000 of his preserving labors. This law is one of the 197 00:13:07.080 --> 00:13:10.600 fundamental principles of chemistry. It is expressed by the greatest 198 00:13:10.720 --> 00:13:14.399 teacher of chemistry as follows quote. If one substance is 199 00:13:14.440 --> 00:13:17.919 transformed into another, then the masses of these two substances 200 00:13:18.000 --> 00:13:21.320 always bear a fixed ratio to each other. If several 201 00:13:21.399 --> 00:13:24.720 substances react together, then their masses, as well as those 202 00:13:24.759 --> 00:13:28.200 of the new bodies formed, always bear fixed proportions to 203 00:13:28.240 --> 00:13:34.200 each other. End quote Oswald Outlines of General Chemistry and dubtedly. 204 00:13:34.240 --> 00:13:37.159 If Prousts had calculated the results of experiments on the 205 00:13:37.159 --> 00:13:42.120 composition of binary compounds sulfide's oxides in another manner from 206 00:13:42.120 --> 00:13:44.440 what he did, he would have discovered the law of 207 00:13:44.519 --> 00:13:48.399 multiple proportions. But the propounding of this is due to Dalton. 208 00:13:49.080 --> 00:13:53.759 John Dalton seventeen sixty six eighteen forty four was born 209 00:13:53.840 --> 00:13:56.600 at Eaglesfield in Cumberland, the son of a poor weaver. 210 00:13:57.480 --> 00:14:01.080 Endowed with natural aptitude in an ende domitable will, he 211 00:14:01.200 --> 00:14:04.399 used all possible opportunities for the study of mathematics and 212 00:14:04.480 --> 00:14:07.960 natural philosophy. From seventeen eighty one to seventeen ninety three 213 00:14:08.039 --> 00:14:12.000 he taught school, instructed and lectured at Kendall, devoted all 214 00:14:12.039 --> 00:14:15.679 the time and energy he could spare to scientific investigations, 215 00:14:16.320 --> 00:14:20.279 chiefly meteorological. In seventeen ninety three he went to Manchester 216 00:14:20.360 --> 00:14:24.879 as tutor of mathematics and natural philosophy at a Presbyterian college. 217 00:14:25.600 --> 00:14:28.320 Though he resigned his post six years later, he remained 218 00:14:28.320 --> 00:14:31.080 in Manchester to the end of his life, earning his 219 00:14:31.159 --> 00:14:35.200 living as a private teacher and devoting himself uninterruptedly and 220 00:14:35.320 --> 00:14:39.919 earnestly to scientific research. The earliest researches of Dalton on 221 00:14:40.000 --> 00:14:43.639 the expansion of gases by heat and their absorption by 222 00:14:43.679 --> 00:14:47.120 liquids were of considerable influence on his later chemical work, 223 00:14:48.000 --> 00:14:50.639 as it was through them that he acquired the experimental 224 00:14:50.679 --> 00:14:53.519 skill which led to the discovery of the law of 225 00:14:53.639 --> 00:14:57.960 multiple proportions, which with the conception of the atomic theory 226 00:14:58.480 --> 00:15:03.000 which arose from it from eighteen oh two. On November twelfth, 227 00:15:03.039 --> 00:15:06.919 eighteen oh two, Dalton read a paper entitled an Experimental 228 00:15:06.960 --> 00:15:10.840 Inquiry into the properties of the several gases or elastic 229 00:15:10.879 --> 00:15:15.120 fluids constituting the atmosphere, on which he found the first 230 00:15:15.159 --> 00:15:18.600 example of the law in determining the amount of oxygen 231 00:15:18.679 --> 00:15:23.240 in the air. The following experiment was performed quote, if 232 00:15:23.240 --> 00:15:25.720 one hundred measures of common air be put to thirty 233 00:15:25.759 --> 00:15:29.679 six pure nitrous gas and a tube three sixteenth of 234 00:15:29.679 --> 00:15:33.600 an inch wide and five inches long. After a few minutes, 235 00:15:33.639 --> 00:15:35.879 the whole will be reduced to seventy nine or eighty 236 00:15:35.919 --> 00:15:40.320 measures and exhibit no signs of either oxygeness or nitrous gas. 237 00:15:41.679 --> 00:15:43.799 If one hundred measures of common air be admitted to 238 00:15:43.840 --> 00:15:47.679 seventy two of nitrous gas in a wide vessel over water, 239 00:15:48.440 --> 00:15:51.279 such as to form a thin stratum of air, and 240 00:15:51.360 --> 00:15:55.919 an intermediate momentary agitation be used, there will, as before 241 00:15:56.039 --> 00:15:59.320 be found seventy nine or eighty measures of pure asiotic 242 00:15:59.360 --> 00:16:04.759 gas nitrogen for a residuum. If in the last experiment 243 00:16:04.960 --> 00:16:07.600 less than seventy two measures of nitrous gas be used, 244 00:16:08.240 --> 00:16:12.000 there will be a residuum containing oxygenous gas. If more 245 00:16:12.039 --> 00:16:16.639 than some residuary nitrous gas will be found, These facts 246 00:16:16.720 --> 00:16:19.840 clowly point out the theory of the process. The elements 247 00:16:19.840 --> 00:16:23.000 of oxygen may combine with a certain portion of nitrous gas, 248 00:16:23.600 --> 00:16:27.440 or with twice that portion, but with no intermediate quantity. 249 00:16:28.240 --> 00:16:31.759 In the former case, nitric acid is the result in 250 00:16:31.799 --> 00:16:35.279 the latter nitrous acid. But as both these may be 251 00:16:35.360 --> 00:16:38.159 formed at the same time, one part of the oxygen 252 00:16:38.240 --> 00:16:41.600 going to one of the nitrous gas and another to two, 253 00:16:42.279 --> 00:16:46.159 the quantity of nitrous gas absorbed should be variable from 254 00:16:46.240 --> 00:16:50.039 thirty six to seventy two percent for common air end quote. 255 00:16:50.399 --> 00:16:55.240 With regard to this experiment, Rosco says, quote and the 256 00:16:55.320 --> 00:16:59.360 memorable case in which Dalton announces the first instance of 257 00:16:59.440 --> 00:17:04.400 combination in multiple proportions, the whole conclusion is based upon 258 00:17:04.640 --> 00:17:09.880 an erroneous experimental basis. If we repeat the experiment as 259 00:17:09.960 --> 00:17:13.119 described by Dalton, we do not obtain the results he 260 00:17:13.279 --> 00:17:18.359 arrived at. We see that Dalton's conclusions were correct, although 261 00:17:18.440 --> 00:17:20.440 in this case it appears to have been a mere 262 00:17:20.559 --> 00:17:25.319 chance that his experimental results rendered such a conclusion possible 263 00:17:25.720 --> 00:17:29.279 end quote. The first that the observations of Dalton, which 264 00:17:29.279 --> 00:17:33.519 furnished the experimental basis for the atomic theory, consisted in 265 00:17:33.559 --> 00:17:37.440 the determination of the composition of two hydrides of carbon 266 00:17:38.319 --> 00:17:42.680 Dalton rites quote. It was in the summer of eighteen 267 00:17:42.720 --> 00:17:45.680 oh four that I collected, at various times and in 268 00:17:45.759 --> 00:17:50.799 various places, the inflammable gas marsh gas, obtained from Pods 269 00:17:51.759 --> 00:17:56.799 end quote. He found that marsh gas, like ollefiant gas ethylene, 270 00:17:57.119 --> 00:18:00.799 contains nothing but carbon and hydrogen, and that these substances, 271 00:18:01.079 --> 00:18:05.440 termed light and heavy carbureted hydrogen, respectively, showed a simple 272 00:18:05.680 --> 00:18:09.559 multiple ratio between the weights of the constituent elements, namely 273 00:18:10.200 --> 00:18:14.160 and carbureted hydrogen from stagnant water. Four point three of 274 00:18:14.240 --> 00:18:18.839 carbon were combined with two of hydrogen. An oleefant gas 275 00:18:19.319 --> 00:18:22.440 four point three of carbon were combined with one of hydrogen. 276 00:18:23.440 --> 00:18:27.039 This regularity induced him to investigate other compounds in the 277 00:18:27.079 --> 00:18:31.599 same direction. Thus, in the case of carbonic oxide and 278 00:18:31.680 --> 00:18:35.720 carbonic acid, he found that for the same amount of carbon, 279 00:18:35.960 --> 00:18:39.799 the ratios of oxygen present, and these were again respectably 280 00:18:40.240 --> 00:18:43.880 as one to two. His convictions that there must be 281 00:18:43.920 --> 00:18:48.480 a law underlying these simple relations scarcely nesitated any further 282 00:18:48.559 --> 00:18:53.640 accretion after he had encountered similar simple numeric proportions, and 283 00:18:53.680 --> 00:18:58.079 the results of his analysis of nitrous oxide, nitric oxide, 284 00:18:58.359 --> 00:19:03.000 nitrous acid, and nitric eas aid in essence the anhydrates 285 00:19:03.039 --> 00:19:06.680 of the last two and the oxygen compounds of sulfur. 286 00:19:07.119 --> 00:19:10.519 He had therefore demonstrated that when different quantities of one 287 00:19:10.559 --> 00:19:14.119 element combined chemically with one of the same quantity of another, 288 00:19:14.839 --> 00:19:17.799 these amounts stood in a simple relation to one another, 289 00:19:18.720 --> 00:19:22.680 a relation which could be expressed with whole numbers. The 290 00:19:22.799 --> 00:19:27.359 law of multiple proportions was thus discovered. It had indeed 291 00:19:27.440 --> 00:19:31.559 been deduced from experiments, which were of necessity not very exact, 292 00:19:32.039 --> 00:19:34.400 but this was to be expected from the condition of 293 00:19:34.480 --> 00:19:38.960 analytical chemistry at that time. Dalton next sought an explanation 294 00:19:39.119 --> 00:19:42.839 of the numerical relations he had discovered, and this was 295 00:19:42.880 --> 00:19:46.880 afforded him by the atomic hypothesis. For instance, he had 296 00:19:47.319 --> 00:19:50.799 but to assume that in carbon monoxide one atom of 297 00:19:50.839 --> 00:19:54.960 carbon was combined with one of oxygen, and in carbonic acid, 298 00:19:55.119 --> 00:19:58.839 one atom of carbon was united to two of oxygen. 299 00:19:59.319 --> 00:20:02.720 Upon his base, systoletly erected is atomic theory, which may 300 00:20:02.759 --> 00:20:06.440 be detailed from statements in his new System of chemical 301 00:20:06.440 --> 00:20:11.799 philosophy eighteen oh eight eighteen ten. As follows number one, 302 00:20:11.920 --> 00:20:15.880 all bodies of sensible magnitude are constituted of a vast 303 00:20:15.960 --> 00:20:19.799 number of extremely small particles or atoms of matter, bound 304 00:20:19.839 --> 00:20:23.119 together by a force of attraction, which, as it endeavors 305 00:20:23.160 --> 00:20:27.519 to prevent their separation, is called attraction of cohesion, but 306 00:20:27.640 --> 00:20:30.720 as it collects them from a dispersed state, is called 307 00:20:30.720 --> 00:20:36.559 attraction of aggregation, or more simply affinity. Number two. The 308 00:20:36.640 --> 00:20:40.599 ultimate particles of all homogeneous bodies are perfectly like in 309 00:20:40.640 --> 00:20:44.440 weight figure et cetera. In other words, every particle of 310 00:20:44.480 --> 00:20:48.440 water is like every other particle of water. Every particle 311 00:20:48.440 --> 00:20:52.160 of hydrogen is like every other particle of hydrogen, et cetera. 312 00:20:52.799 --> 00:20:56.720 Number three, No new creation or destruction of matter is 313 00:20:56.759 --> 00:21:00.279 within the reach of chemical agency. All ye elements we 314 00:21:00.319 --> 00:21:04.640 can produce consist in separating particles that are in a 315 00:21:04.680 --> 00:21:08.640 state of cohesion or combination and joining those that were 316 00:21:08.680 --> 00:21:12.759 previously at a distance. Number four. The ultimate particles of 317 00:21:12.799 --> 00:21:17.480 all simple bodies are atoms, incapable of feather division. These atoms, 318 00:21:17.880 --> 00:21:21.640 at least viewed along with their atmospheres of heat, are 319 00:21:21.680 --> 00:21:25.519 all spheres, and are possessed of particular weights, which may 320 00:21:25.559 --> 00:21:30.119 be denoted by numbers number five. If there are two 321 00:21:30.200 --> 00:21:34.240 bodies which are disposed to combine, then their combination takes 322 00:21:34.240 --> 00:21:40.160 place by atoms number six. In an elastic gas, each 323 00:21:40.200 --> 00:21:44.599 particle occupies the center of a comparatively large sphere and 324 00:21:44.640 --> 00:21:48.119 supports its dignity by keeping all the rest which, by 325 00:21:48.160 --> 00:21:51.960 their gravity or otherwise are disposed to encroach upon it 326 00:21:52.640 --> 00:21:56.599 at a respectful distance. The methods by which Dalton determine 327 00:21:56.599 --> 00:21:59.839 the relative atomic weights from the proportions by weight in 328 00:22:00.079 --> 00:22:03.279 which the elements unite to form compounds falls next to 329 00:22:03.319 --> 00:22:07.519 be described. To accomplish this, the first thing necessary was 330 00:22:07.559 --> 00:22:11.319 to settle the number of atoms in a compound. According 331 00:22:11.359 --> 00:22:13.960 to Dalton, this number is to be sought for in 332 00:22:14.039 --> 00:22:18.640 general in the simplest possible ratios. In estimating it, he 333 00:22:18.799 --> 00:22:23.640 started from the following principles. Number one, When only one 334 00:22:23.680 --> 00:22:26.920 compound of two elements is known, this is composed of 335 00:22:26.960 --> 00:22:30.839 an atom of the second order. Number two. When two 336 00:22:30.880 --> 00:22:34.119 compounds are known, the one consists of an atom of 337 00:22:34.160 --> 00:22:36.839 the second and the other of an atom of the 338 00:22:36.920 --> 00:22:41.920 third order. Number three. When three compounds are known, one 339 00:22:42.039 --> 00:22:45.039 atom of the second and two atoms of the third 340 00:22:45.160 --> 00:22:48.839 order must be assumed. How did Dalton, I'll proceed to 341 00:22:48.920 --> 00:22:53.160 the determination of the atomic weights, in essence, the relative 342 00:22:53.160 --> 00:22:56.319 weights of the smallest particles. In the first place, it 343 00:22:56.400 --> 00:23:00.440 was necessary to choose a unit for comparisons. Unit He 344 00:23:00.519 --> 00:23:04.240 assumed hydrogen, but the atomic weight equals one, and he 345 00:23:04.279 --> 00:23:07.720 referred all the other atomic weights to this. To fix 346 00:23:07.759 --> 00:23:11.319 the others. He then applied his first principle. At that time, 347 00:23:11.359 --> 00:23:14.839 only one compound each of oxygen and if nitrogen with 348 00:23:14.960 --> 00:23:20.839 hydrogen was known, namely water and ammonia, respectively. Therefore, the 349 00:23:20.880 --> 00:23:24.640 atomic weights of oxygen and nitrogen can be determined directly 350 00:23:24.680 --> 00:23:28.480 from the composition of these compounds. In this way, Dalton 351 00:23:28.519 --> 00:23:31.920 found them to be seven and five, respectively. He checked 352 00:23:31.960 --> 00:23:34.960 the numbers so obtained by the proportions of the oxygen 353 00:23:35.000 --> 00:23:39.200 and nitrogen. In the oxygen compounds. Of nitrogen, he was 354 00:23:39.240 --> 00:23:43.240 acquainted with four of the latter. In nitrogoxide, he found 355 00:23:43.279 --> 00:23:47.240 seven parts of oxygen for five of nitrogen. Its atom 356 00:23:47.400 --> 00:23:50.480 was therefore the atom of the second order derived from 357 00:23:50.519 --> 00:23:55.400 these elements. In nitric acid, according to his view, there 358 00:23:55.400 --> 00:23:59.160 were fourteen parts of oxygen for five of nitrogen, or 359 00:23:59.200 --> 00:24:01.880 two atoms of the former gas for one of the latter. 360 00:24:02.720 --> 00:24:06.799 In nitrous oxide, seven parts of oxygen were combined with 361 00:24:06.839 --> 00:24:10.359 ten parts of nitrogen, and in this he therefore assumed 362 00:24:10.680 --> 00:24:14.920 two atoms of nitrogen and one of oxygen. Nitrous acid, however, 363 00:24:15.000 --> 00:24:17.400 is supposed to contain ten and a half parts of 364 00:24:17.440 --> 00:24:21.599 oxygen for five of nitrogen, and in it he might 365 00:24:21.640 --> 00:24:24.480 have assumed two atoms of nitrogen and three of oxygen. 366 00:24:25.279 --> 00:24:28.440 He preferred, however, to regard the substance as a compound 367 00:24:28.440 --> 00:24:32.759 of nitric acid and nitric oxide. Likewise, he found an 368 00:24:32.759 --> 00:24:36.359 ethylene five point four parts of carbon for one of hydrogen, 369 00:24:36.960 --> 00:24:39.599 and in marsh gas the same quantity of carbon for 370 00:24:39.640 --> 00:24:44.160 two of hydrogen. On this account, he regarded ethylene as 371 00:24:44.200 --> 00:24:47.680 consisting of atoms of the second order, and assumed the 372 00:24:47.720 --> 00:24:51.640 atomic weights of carbon to be five point four. Carbonic 373 00:24:51.839 --> 00:24:55.880 Oxide likewise consisted of atoms of the second order, since 374 00:24:55.920 --> 00:24:58.799 he found in it seven parts of oxygen for five 375 00:24:58.839 --> 00:25:03.640 point four of carbon, while carbonic anhydride and atoms of 376 00:25:03.680 --> 00:25:07.119 the third order because it contains fourteen parts of oxygen 377 00:25:07.880 --> 00:25:11.559 for five point four of carbon. As the analytical methods 378 00:25:11.559 --> 00:25:15.880 of Dalton employed reliable to many sources of error, it 379 00:25:16.000 --> 00:25:18.680 was out of the question that the results he obtained 380 00:25:18.960 --> 00:25:23.000 could be accurate. However, it was he who propounded the 381 00:25:23.039 --> 00:25:26.720 principle of the determination of the combining weights of the elements, 382 00:25:27.200 --> 00:25:31.519 and this work brought him everlasting fame. Dalton's atomic theory, 383 00:25:31.799 --> 00:25:37.400 generally speaking, was favorably received by chemists. Thomas Thompson seventeen 384 00:25:37.440 --> 00:25:41.279 seventy three eighteen fifty two, who founded the first chemical 385 00:25:41.359 --> 00:25:45.119 laboratory for general instructions in Great Britain while professor in 386 00:25:45.200 --> 00:25:49.599 the University of Glasgow, became its devouted supporter, and his 387 00:25:49.759 --> 00:25:53.119 system of chemistry eighteen o seven made it known to 388 00:25:53.160 --> 00:25:57.119 the general public. In eighteen oh eight, Thompson supplied an 389 00:25:57.119 --> 00:25:59.880 observation of his own in support of the law of 390 00:26:00.079 --> 00:26:05.720 multiple proportions. Dalton's attempts at a graphic presentation of the 391 00:26:05.799 --> 00:26:10.119 ultimate particles of various substances must not be forgotten. The 392 00:26:10.160 --> 00:26:12.880 symbols he used to represent the atoms of the elements 393 00:26:13.400 --> 00:26:18.039 and to indicate the constitution of chemical compounds, as well 394 00:26:18.079 --> 00:26:22.880 as his relative weight values, are here given. This system 395 00:26:22.920 --> 00:26:26.079 of notation never came into general use, owing to the 396 00:26:26.119 --> 00:26:30.519 introduction of a simpler system by Brazilius sometime afterward. To 397 00:26:30.599 --> 00:26:34.160 quote his own inference, it appears that there are two 398 00:26:34.359 --> 00:26:40.000 oxalates of strontium, the first obtained by saturating hogxalic acid 399 00:26:40.359 --> 00:26:45.200 with strontium water, the second by mixing together oxalate of 400 00:26:45.200 --> 00:26:51.000 ammonia and mariate chloride of strontium. It is remarkable that 401 00:26:51.039 --> 00:26:54.359