Oxygen. ... 22.22 77.77 Hence, then, it must be considered in the light of a pure chemical compound; and indeed nothing but this supposition will account for its uniformity all over the world, as demonstrated by numerous experiments. From these data the specific gravities of oxygen and azote (atmospheric air being 1·000) will be found to be,* Oxygen 1.1111 9722 2. Hydrogen. The specific gravity of hydrogen, on account of its great levity, and the obstinacy with which it retains water, has always been considered as the most difficult to take of any other gas. These obstacles made me (to speak in the first person) despair of arriving at a more just conclusion than had been before obtained by the usual process of weighing; and it occurred to me that its specific gravity might be much more accurately obtained by calculation from the specific gravity of a denser compound into which it entered in a known proportion. Ammoniacal gas appeared to be the best suited to my purpose, as its specific gravity had been taken with great care by Sir H. Davy, and the chance of error had been much diminished from the slight difference between its sp. gr. and that of steam. Moreover, Biot and Arrago had obtained almost precisely the same result as Sir H. Davy. The sp. gr. of ammonia, according to Sir H. Davy, is 590164, atmospheric air being 1.000. We shall consider it as 5902; and this we are authorized in doing, as Biot and Arrago state it somewhat higher than Sir H. Davy. Now ammonia consists of three volumes of hydrogen and one volume of azote condensed into two volumes. Hence the sp. gr. of hydrogen will be found to be '0694,† atmospheric air being 10000. It will be also observed that the sp. gr. of oxygen as obtained above is just 16 times that of hydrogen as now ascertained, and the sp. gr. of azote just 14 times. ‡ 3. Chlorine. The specific gravity of muriatic acid, according to Sir H. Davy's experiments, which coincide exactly with those of Biot and Arrago, is 1.278. Now if we suppose this sp. gr. to be erroneous in the same proportion that we found the sp. gr. of oxygen and azote to be above, (which, though not rigidly accurate, may yet be fairly done, since the experiments were conducted in a similar manner), the sp. gr. of this gas will come out about 1.2845;* and since it is a compound of one volume chlorine and one volume hydrogen, the specific gravity of chlorine will be found by calculation to be 2.5.† Dr. Thomson states, that he has found 2:483 to be near the truth, ‡ and Gay-Lussac almost coincides with him. § Hence there is every reason for concluding that the sp. gr. of chlorine does not differ much from 2.5. On this supposition, the sp. gr. of chlorine will be found exactly 36 times that of hydrogen. On the Specific Gravities of Elementary Substances in a Gaseous State that do not at ordinary Temperatures exist in that State. 1. Iodine.--I had some reason to suspect that M. Gay-Lussac had in his excellent memoir rated the weight of an atom of this substance somewhat too high; and in order to prove this 50 grains of iodine, which had been distilled from lime, were digested with 30 grs. of very pure lamellated zinc. The solution formed was transparent and colourless; and it was found that 12.9 grains of zine had been dissolved. 100 parts of iodine, therefore, according to this experiment, will combine with 25-8 parts of zinc, and the weight of an atom of iodine will be 155, zinc being supposed to be 40. From these data, the sp. gr. of iodine in a state of gas will be found by calculation to be 8.611111, or exactly 124 times that of hydrogen.* ** 2. Carbon. I assume the weight of an atom of carbon at 7.5. Hence the sp. gr. of a volume of it in a state of gas will be found by calculation to be 4166, or exactly 12 times that of hydrogen. 3. Sulphur.-The weight of an atom of sulphur is 20. Hence the specific gravity of its gas is the same as that of oxygen, or 1∙1111, and consequently just 16 times that of hydrogen. *As 1-104: 1·11111 :: 1·278: 1.286. And as 969 : ·9722 :: 1·278: 1.283. The mean of these is 1.2845. + Let x = sp. gr. of chlorine. Then x+0694 2 1.2845. And x = 2.5690694 Annals of Philosophy, vol. iv. p. 13. Ditto, vol. vi. p. 126. As 25'8 100 :: 40: 155. According to experiment 8th, stated below, the weight of an atom of zinc is 40. Dr. Thomson makes it 40.9, which differs very little. See Annals of Philosophy, vol. iv. p. 94. ** One volume of hydrogen combines, with only half a volume of oxygen, but with a whole volume of gaseous iodine, according to M. Gay-Lussac. The ratio in volume, therefore, between oxygen and iodine is as to 1, and the ratio in weight is as 1 to 15.5. Now 5555, the density of half a volume of Oxygen, multiplied by 15 5, gives 8-61111, and 8-611106944 124. Or generally, to find the sp. gr. of any substance in a state of gas, we have only to multiply half the sp. gr. of oxygen by the weight of the atom of the substances with respect to @xygen. See Annals of Philosophy, vol. v. p. 105. 4. Phosphorus.-I have made many experiments in order to ascer tain the weight of an atom of this substance; but, after all, have not been able to satisfy myself, and want of leisure will not permit me to pursue the subject further at present. The results I have obtained approached nearly to those given by Dr. Wollaston, which I am therefore satisfied are correct, or nearly so, and which fix phosphorus at about 17.5, and phosphoric acid at 37·5,* and these numbers at present I adopt. 5. Calcium.-Dr. Marcet found carbonate of lime composed of 43.9 carbonic acid and 56°1 lime. † Hence as 43.9: 56°1 :: 27.5 :35 1, or 35 very nearly; and 35 10 25, for the atom of calcium. The sp. gr. of a volume of its gas will therefore be 1:3888, or exactly 20 times that of hydrogen. 6. Sodium.-100 grains of dilute muriatic acid dissolved 18.6 grs. of carbonate of lime, and the same quantity of the same dilute acid dissolved only 8.2 grs. of carbonate of lime, after there had been previously added 30 grs. of a very pure crystallized subcarbonate of soda. Hence 30 grs. of crystallized subcarbonate of soda are equivalent to 104 grs. of carbonate of lime, and as 10·4 : 30 :: 62·5 : 180. Now 100 grs. of crystallized subcarbonate of soda were found by application of heat to lose 62.5 of water. Hence 180 grs. of the same salt contain 112-5 water, equal to 10 atoms, and 67.5 dry subcarbonate of soda, and 67.5 27.5 40 for the atom of soda, and 40 10 = 30 for the atom of sodium. Hence a volume of it in a gascous state will weigh 1.6666, or exactly 24 times that of hydrogen. 7. Iron.—100 grs. of dilute muriatic acid dissolved as before 18.6 grs. of carbonate of lime, and the same quantity of the same acid dissolved 10:45 of iron. Hence as 18.6: 10·45 :: 62·5: 35·1, or for the sake of analogy, 35, the weight of an atom of iron. The sp. gr. of a volume of this metal in a gaseous state will be 1.9444, or exactly 28 times that of hydrogen. 8. Zinc.-100 grs. of the same dilute acid dissolved, as before, 18.6 of carbonate of lime and 11.85 of zine. Hence as 18.6 : 11.85 :: 62.5 39.82, the weight of the atom of zinc, considered from analogy to be 40. Hence the sp. gr. of a volume of it in a gaseous state will be 2.222, or exactly 32 times that of hydrogen. 9. Potassium.-100 grs. of the same dilute acid dissolved, as before, 18.6 carbonate of lime; but after the addition of 20 grs. of supercarbonate of potash, only 8.7 carbonate of lime. Hence 20 grs. of super-carbonate of potash are equivalent to 9.9 carbonate of lime; and as 9.9: 20 :: 62·5: 126.26, the weight of the atom of supercarbonate of potash. Now 126.26 55 + 11:25 = 60, the Some of my experiments approached nearer to 20 phosphorus and 40 phos phoric acid. + I quote on the authority of Dr. Thomson, Annals of Philosophy. vol. iit.' p. 376. Dr. Wollaston makes it somewhat different, or that carbonate of lime consists of 43.7 acid and 56.3 lime, Phil. Trans. vol. civ. p. 8. weight of the atom of potash, and 60 10 50, the weight of the atom of potassium. Hence a volume of it in a state of gas will weigh 2-7777, or exactly 40 times as much as hydrogen. 10. Barytium.-100 grs. of the same dilute acid dissolved exactly as much again of carbonate of barytes as of carbonate of lime. Hence the weight of the atom of carbonate of barytes is 125; and 125 275 97.5, the weight of the atom of barytes, and 97.5 10 87.5, the weight of the atom of barytium. The sp. gr. therefore, of a volume of its gas will be 4.8611, or exactly 70 times that of hydrogen. = With respect to the above experiments, I may add, that they were made with the greatest possible attention to accuracy, and most of them were many times repeated with almost precisely the same results. The following tables exhibit a general view of the above results, and at the same time the proportions, both in volume and weight, in which they unite with oxygen and hydrogen: alse the weights of other substances, which have not been rigidly examined, are here stated from analogy. |