444 Mr. Dalton on the Vis Viva. [Dec. 



agitated in barytes water, no immediate precipitate takes place ; 

 though if we boil the mixture, a dirty grey precipitate at last 

 falls. 



When the compound is heated, it becomes soft and ductile ; 

 but requires for fusion a higher temperature than sulphur. But 

 if the heat be continued, a kind of effervescence takes place, and 

 the compound is converted into common sulphur, which burns 

 in the usual manner. 



When the compound is agitated with water, that liquid 

 becomes milky, acquires a slightly acidulous taste, and a quan- 

 tity of common sulphur is speedily deposited. The very same 

 decomposition is produced by alcohol. 



With potash it does not combine unless water be present, and 

 in that case nothing is formed but common sulphuret of potash. 



I have tried the action of various other re-agents upon this 

 compound ; but the phenomena presented were so little remark- 

 able that they seem scarcely entitled to be related. 



This is, perhaps, the first acid compound hitherto observed 

 which contains both oxygen and hydrogen united to a combus- 

 tible basis. Though of little importance in a practical point of 

 view, it is of some little value as far as the theory is concerned ; 

 for it possesses the properties of acidity in a very weak degree, 

 so much so that I have not been able to succeed in uniting it with 

 any salifiable basis. This, I think, is a sufficient proof that 

 Dr. Murray's notion, that the greatest degree of acidity is given 

 to bodies by the joint union of oxygen and hydrogen, is not coun- 

 tenanced by chemical facts, nor consistent with the phenomena 

 of the science. 



I have not given this new compound a name, because it is not 

 likely ever to be employed for any useful purpose. Perhaps the 

 term hydrosulphurous acid, though not quite correct, might be 

 applied to it without much impropriety. 



Article VI. 



On the Vis Viva. By Mr. John Dalton. 



(To Dr. Thomson.) 



RESPECTED FRIEND, Manchester, Oct. 12, 1818. 



In the Annales de Chimie et de Physique for last July, there 

 is a paper by M. Petit on the employment of the principle of the 

 vis viva in the calculation of the effects of machines. 



M. Petit expresses his surprise that so little attention has 

 hitherto been paid to this principle, which he considers to be 

 capable of general and highly interesting application. He 

 observes, the theory of machines considered with reference to tins 



