248 Sir H. Davy's fisrther Observations 



_inuriatic acid, destroyed the colour of the same quantity of the 

 blue liquor. 



On this circumstance it was easy to found a method of deter- 

 mining the precise quantity of chlorine produced in solution 

 of muriatic acid, from a given quantity of the compound ; 

 namely, by comparing the power of a given quantity of mu- 

 riatic acid, containing a known quantity of chlorine, to destroy 

 the colour of solutions of indigo, with that of the muriatic acid, 

 in which the compound had produced chlorine. 



Two experiments were made. In the first, a grain of the 

 compound was exposed on a large surface beneath a tube in- 

 verted in about six cubic inches of solution of muriatic acid, 

 and the chlorine absorbed by agitation as it was formed. The 

 acid so treated destroyed the colour of seven cubic inches of 

 a diluted sulphuric solution of indigo ; and it was found, by 

 several comparative trials, that exactly the same effect was 

 produced in another equal portion of the same solution of in- 

 digo, by 2, a cubic inches of chlorine dissolved in the same 

 quantity of muriatic acid. 



In the second experiment, 1,3 cubic inches of chlorine 

 were evolved in the gaseous form, the thermometer being 

 at 58^ and barometer at 30,33, and suffered to pass into the 

 atmosphere ; and by the test of the solution of indigo, it 

 was found that ,75 pf a cubic inch remained dissolved in the 

 acid. 



Now, if the mean of these two experiments be taken, it 

 appears that %,6i grains of chlorine are produced in solution 

 of muriatic acid by the action of a grain of the compound; and 

 calculating on the data just now referred to, the compound 

 must consist of 91 of chlorine and 9 of azote in weight, which 



