On the Decompofilion of Muriatic Acid, 375 



been volatilized during its folution of the tin, and carried off by the hydrogen gas during its 

 efcape, this cannot be fuppofed to account for more than a very fmall proportion of the acid 

 which difappeared. I therefore infer that when tin is diflblved in muriatic acid, a part of 

 the acid is decompofed, and I think it not improbable that, it fupplies the tin with oxygen, 

 and that its other component part hydrogen flies oiF in the form of hydrogen gas. I am • 

 well aware that many more experiments ought to be tried before it can be eftabliflied that 

 oxygen and hydrogen are the conftituent principles of muriatic acid ; but one thing is I 

 think fully eftabliflied by this experiment,' namely, that fome portion of this acid is decom- 

 pofed during the folution of tin; For if in Dr. Fordyce's experiment, in which two equal 

 portions of fulphuric acid, in one of which zinc had been diflblved, and in the other not, 

 required equal quantities of pot-afh to faturate them, it was a fair inference, that therefore 

 fulphuric acid is not decompofed in diflblving zinc ; it is equally fair to infer from my experi- 

 ment in which the muriatic acid, in which tin had been diflblved, required fo much lefs pot- 

 a(h to faturate it than an equal quantity of the fame acid in which no tin had been diflblved, 

 that part of the muriatic acid is decompofed in diflblving tin. 



I am alfo fenfible that the above experiment might be tried in a much better way : the 

 quantity of water contained In the muriatic acid ought to be afcertained previous to the fo- 

 lution of the tin, and after its precipitation by the alkali, and a calculation then made, 

 whether the portion of water mifling would account for all the hydrogen and oxygen pro- 

 duced : if it appeared that the quantities of thefe were greater than the water mifling would 

 furnifli, then I think it would be eftabliflied that they entered into the compofition of mu- 

 riatic acid. Another important experiment would be to expofe tin to muriatic acid gas, 

 perfectly free from water (a method of obtaining, which appears in Mr. Henry's experi- 

 ments, and will be hereafter mentioned), and examine whether it becomes oxidated, and 

 to expofe not only tin but every other metal, and every other fubft;ance, likely to feparate 

 the oxygen of this acid from the unknown radical. I am neither in pofl"efl!ion of an appara- 

 tus fufliciently delicate, nor have I opportunity at prefent to try thefe and fimilar experi- 

 ments, but having feen in the Philofophical Tranfaftions for i8co, page 188, that Mr. 

 William Henry has been engaged in experiments on the decompofition of this acid, I have 

 thought it right to fuggefl the above hints. 



The chemical world has great obligations to Mr. Henry for the labour and patience he 

 mufl; have expended on his very interefting experiments. I fliould wifli to be permitted to 

 make a few obfervations which refulted from an attentive perufal of his paper. 



The firfl; ferics of his experiments confifted in pafling. the ele£tric fliock repeatedly , 



through muriatic acid gas confined over mercury. The eflfefl; was the diminution of this ^ 



gas, the produflion of hydrogen gas, and the oxidation of the furface of the mercury : all 

 this he attributes not to any decompofition of the acid, but to that of the water, which in 

 the dryefl: form, in which the gas is ufually produced, flill adheres to it. As thefe efl!e£ls 

 took place only for a limited time, after which continued ele£lrifation produced them 

 no longer, and as a portion of muriatic acid gas always remained entire, this inference 



is> 



