On definite Fruportions. 199 



hence too the sulphuric acid, a combination of two strongly 

 negaiive sul)sianct.'s, is the strongest, that is, the most 

 negative of" all aciils, with rtspect to all salifiable bases, 

 .May not ihe appearance oF fire be derived trom an electro- 

 chemical discharge ? Much may be adduced in favour of 

 this opinion from Davy's excellent investigations : it appears 

 to mc to be by no means an improbable one, and Davy 

 himself seems to have hinted at it. 



If copper bears the same relation to sulphur and oxygen 

 that lead does, it must absorb, at its minimum of oxida- 

 tion, half as much oxvgcn as it takes up of sulphur, that 

 is, 12 8 or 13 per cent, of oxygen, and the sulphate of the 

 protoxide of copper must consist of 35 S3 of acid with 

 64-17 of the protoxide. And if the sulphuric acid requires, 

 in the bases by which it is saiurited, always half as much . 

 oxygen as it contains of sulphur, the sulphate of the oxide 

 of copper must consist of nearly equal parts of the acid 

 and of the base. 



V. Copper and Oxygen. 



A. Oxide of Ccpper. 



1.) Ten grammes of copper, rolled into a very thin plate, 

 were burnt m the muffle of an assayins furnace in a crucible 

 of platina. The metal was changed into black oxide, and 

 had acquired the additional weight of 105 grammes. 



2.) Five grammes of copper were dissolved in nitric 

 acid in a glass flask, then dried and ignited : they afforded 

 O'lQ of black oxide of copper. 



3.) Anotlier experiment gave 6*145 of oxide. 



4.) Ten grammes of copper were dissolvtd in nitric acid, 

 and precipitated with neutral carbonate of potass, which 

 had been prepared in a vessel of platina from purified tartar. 

 The precipitate, when washed and ignited, weighed 12 33 

 gr. From the fluid, to which the alkali had been added, 

 8ome more copper was thrown dow n by sulphuretted h\ dro- 

 gen, which, when burnt to a black oxide, weighed -08 gr. 

 Diaking with the former IS'll gr. 



5.) The same quantity of copper was dissolved in nitric 

 ^cid ill a glass retort; the ;icid was carefully di-;tdled off to 

 dryness, and the mass left ii» il)e retort, when ignited, 

 weighed 12"3S gr. The acid which iiad passed over was 

 cjistilled again, and the green fluid which was left behind 

 afforded a precipitate, by the successive addition of alkali 

 and of sulphuretted hydrogen, which aff )rded -07 gr. niorej 

 ef black oxide, making with the former 12"45 grammes. 



It i» dillicuU to obtain in these exp^nmems a very accu- 

 N 4 rate 



