. Detection of Adulterations, 79 



eight tenths of an inch in diameter, and containing a mixture of lime 

 and water. A lamp heat being now applied to the matrass, until the 

 whole length of the tube passing from it becomes warm, chlorine 

 will be formed, and absorbed by the lime, which will thus be con- 

 verted into a chloride of lime. This solution of the chloride is then 

 to be diluted with water, until its quantity be 2.113 wine pints, and 

 its strength is then to be ascertained.* This will determine the 

 quantity of pure peroxide contained in the portion examined } since, 

 if the solution be found to have contained 0.9 its volume of chlorine, 

 the quantity of pure oxide will be 0.9 of the portion examined, and 

 the number 0.9 will represent the purity of the specimen. To ascer- 

 tain how much hydrochloric acid has been expended but not convert- 

 ed to chlorine, it is necessary to subtract from the whole quantity 

 employed, that converted into chlorine and chloride of manganese. 

 Now the quantity of chlorine liberated is precisely the same as that 

 absorbed by the protoxide of manganese, in the form of hydrochlo- 

 ric acid ; and one part of pure peroxide of manganese completely 

 decomposes 1.628 of pure and dry hydrochloric acid. Consequent- 

 ly, to know the quantity of acid decomposed by the pure peroxide 

 alone of any specimen, we have only to multiply the number 1.628 

 by the number representing the purity of the specimen. 



The quantity of hydrochloric acid originally poured upon the ox- 

 ide includes that converted to chlorine, besides the portions which 

 combine with the protoxide of manganese and its various impurities,, 

 and with the lime. To determine the quantity of absolute acid in 

 this, take a similar quantity of the same, and after moderate dilution, 

 add a known weight of marble. The quantity of marble dissolv- 

 ed will indicate the quantity of dry acid ; one hundred grains of mar- 

 ble corresponding to seventy-four grains of absolute acid. 



Repeat the first part of the process already given for ascertaining 

 the quantity of chlorine furnished by the oxide ; but observe that the 

 gas must be received into water ; instead of the mixture of lime and 

 water used in the first instance. Then add the water which has re- 



* This is known by the quantity of the sulphuric solution of indigo the color of 

 which it can destroy. The solution is made by finely pulverizing good indigo, sift- 

 ing it through silk, and heating it for six or eight hours on the sand bath, with nine 

 times its weight of sulphuric acid sp. gr. 1.848. We must then ascertain how much 

 chlorine is required to destroy its color, and carefully dilute it just so far that the col- 

 or of ten volumes will be destroyed by a solution containing one volume of chlorine. 



