1 8 1 S/J On the Nature of Muriatic Acid. 257 



muriatic acid gas, there is always a sufficient quantity of oxygen 

 present to convert the potassium into potash, without decom- 

 posing a single atom of muriatic acid. 



But there are methods, less direct indeed, but not less sure, 

 of coming to a decisive conclusion on this point. The doctrine 

 of definite proportions affords us the means of calculating what 

 cannot come directly under our hands; just as the astronomers 

 have made the most striking discoveries by means of mathema- 

 tical calculations. You entertain no doubts, I hope, respecting 

 the truth of that doctrine. Now I shall show from it that there 

 are combinations which, if explained according to the hypothesis 

 of Davy, are inconsistent with well ascertained chemical propor- 

 tions. 



Such are all the submuriates which contain water of combina- 

 tion. I have proved by a set of experiments (which you will 

 find in the Annates de Chimie for May and June 1812) that 

 when a salt contains combined water, that water always exists in 

 such a proportion that its oxygen is always either equal to that 

 of the base, or it is a multiple or submultiple of it by a whole 

 number. For example, the subsulphate of iron contains a 

 quantity of water whose oxygen is equal to that of the oxvgen in 

 the oxide of iron, which constitutes the base of the salt". The 

 subsulphate of copper is so constituted that the water, the acid, 

 and the oxide, contain each the same quantity of oxygen. 

 Hence we'may conceive this salt to be composed of one atom of 

 acid and three atom of hydrate of copper. The new hypothesis 

 admits the existence of a submuriate of copper. Let us examine 

 the composition of this salt. We obtain the salt by pourino- 

 caustic alkali into the muriate of copper, taking care not to 

 precipitate the whole of the oxide from the solution. The pre- 

 cipitate well washed and dried is the submuriate of copper. If 

 we dissolve it in nitric acid, and precipitate the muriatic acid by 

 nitrate of silver, we obtain a quantity of muriate of silver, 

 indicating 12-1 parts of muriatic acid in 100 parts of the sub- 

 muriate of copper. Digest the liquid over mercury to get rid 

 of the superfluous silver- evaporate to dryness in a platinum 

 crucible, and expose it to a red heat till all the acid and mercury 

 are driven off: the oxide of cupper obtained weighs 72 parts. 

 Ihus the acid and base in 100 parts of submuriate of coppei 

 amount to 84*1 parts. The 15-9 parts wanting must have been 

 combined water. We may ascertain the existence of this water 

 by heating the submuriate in a retort previously weighed, and 

 furnished with a tube filled with muriate of lime. The subsalt, 

 together with its water, loses a little oxygen gas which passes 

 UWMigh the muriate of lime, leaving the water behind it In 

 this manner we obtain from 15-75 to 16 parts of water, accord- 

 ing as the submuriate has been more or less perfectly dried If 



Vol. II. N° IV. R 



