1S13.] On the Specific Qi-avky of the Gases. ' ISI 



Ixxi. p. 262), which seem to have been made with great accu- 

 racy. They diifcr but little from the preceding experiments of 

 Kirwan. Allan and Pepys found the specific gravity of this gas 

 1-524. 



] 2. 1 have given the specific gravity of muriatic acid accord- 

 ing to the late experiments of Sir Humphry Davy. They 

 coincide exactly with those of Biot and Arrago. This exact 

 coincidence I consider as a strong proof of accuracy. Mr. 

 Kirvvan's previous estimate, founded on calculation, was not 

 entitled to confidence. 



13. The specific gravity of sulphureted hydrogen gas is 

 according to the late determination of Sir Humphry Davy 

 (Phil. Trans. 1812, part 2d). We had two ])revious determina- 

 tions : one by Kirwan, that it was I'lOG; another by Thenard, 

 that it was 1*236. If this gas be obtained from sulphuret of 

 iron it is always mixed with hydrogen gas. Some such mixture 

 may have occasioned Kirvvan's mistake. It is not so easy to 

 account for the error of Thenard. 



M. The specific gravity of oxygen gas, as ascertained by 

 Saussure, is in all probability pretty near accuracy. He makes 

 it l'U4 (Ann. de Chim. vol. Ixxi. p. 260). Kirwan, Lavoisier, 

 Biot, and Arrago, make the specific gravity of this gas 1-103. 

 Messrs. Allan and Pepys make it 1*090^ and Sir Humphry 

 Davy, in his Besearches, makes it as high as 1*127. The result 

 of the experiments of Fourcroy, Vauquelin, and Seguin, coin- 

 cidfis very nearly with the subsequent experiments of Allan and 

 Pepys. They found it 1*087. The mean of all these experi- 

 ments is 1'104; and we have little doubt that this result is very 

 near tlie truth. On that account it has been inserted in the 

 table. 



15. The specific gravity of nitrous gas is given according to 

 the results obtained by Berard, and published by Gay-Lussac. 

 if Gay-Lussac's statement, that it is composed of equal bulks 

 of oxygen and azotic gas without any condensation, be true, 

 then its sj)ecific gravity ought to be 1*0375, which differs but 

 little from that given in the table. Sir Humphry Davy, in his 

 Researches, makes it as high as 1*094. 



16. The specific gravity of olefiant gas is the result of my 

 own experiments. They have been published in the first volume 

 of the Transactions 9f the Wernerian Society of Edinburgh. 



17. The specific gravity of azote, as given in the table, is the 

 result of the experiments of Biot and Arrago. If we suppose 

 the specific gravity of air 1, of oxygen 1*104, and that air is a 

 mixture of 7^ parts by bulk of azote, and 21 of oxygen, then 

 the specific gravity of azote by calculation comes out 0'9'J23^ 

 7'his docs not differ much from the number in the table. 



