412 Account of a New Hydraulic Machine. [Dec. 



oxide of zinc is composed of 82-859 metal + 2002 oxygen, or 

 of 100 metal + 24 16' oxygen. 



The preceding experiments warrant us, 1 conceive, to consider 

 the oxide of zinc as composed of 100 metal + 24-16' oxygen. 

 Now this determination approaches much nearer to that of Ber- 

 zelius, who found oxide of zinc composed of 100 metal + 24-4 

 oxygen ; than to that of Sir H. Davy, who makes it 100 metal 

 + 21-951 oxygen; or myself, who obtained the numbers 100 

 metal + 23-5 oxygen, by direct experiment. This new deter- 

 mination of the" composition of the oxide of zinc makes it 

 necessary to alter the numbers representing the weight of an 

 atom of zinc in the table {Annals of Philosophy), vol. ii. p. 49). 

 Instead of 4*315, the corrected number will be 4*139, and the 

 weight of the oxide of zinc will he 5-139. 



These new numbers do not agree quite so well with my ana- 

 lysis of the suiphate of zinc (stated iu the Annals of Philosophy, 

 vol. ii. p. 29/ .%as the preceding ones, which I employed in my 

 table. I found sulphate of zinc composed of 25-8 acid + 282 

 oxide. Now 5 (the weight of an atom of acid) : 5-139 (the 

 weight of an atom of oxide) :: 2.V8 : 265 17. But I find, upon 

 considering my analysis, that the quantity of sulphuric acid 

 obtained is underrated. 100 grains of crystallized sulphate of 

 zinc yielded 7^2 grains of sulphate of barytes. Now 7#'2 of 

 sulphate of barytes contain, according to the analysis of Berze- 

 lius, 266 of sulphuric acid. Now 5 : 5-139 :: 26-6 : 27*34. 

 This does not exactly coincide with the 28-2 of oxide of zinc 

 obtained. But 1 find two circumstances stated in the account of 

 my analysis which appear to me quite sufficient to account for 

 the difference. 1 . The sulphate of zinc which I analyzed is 

 stated to redden vegetable blues. Now 1 find that the salt 

 obtained by dissolving zinc in sulphuric acid has not that pro- 

 perty. Hence the salt analyzed must have contained a slight 

 excess of acid. 2. The precipitate of oxide of zinc is described 

 as flesh coloured. This shows that it was mixed with iron, and 

 consequently that the salt was not quite pure. 



Article IV. 



Account of a New Hydraulic Machine. Contrived by M, 



Mannoury Dectot.* 



The Class has already approved of several machines invented 



• This is a translation of the Report made to the Institute on the subject on 

 the 23d August, 1813. I have translated it from the Moniteur of the 27tb 

 August. 



