254 GUNPOWDEK. 



lence of the combustion. The mixture is introduced 

 into a platinum crucible, and heated to redness over a 

 large spirit-lamp or gas-burner. Near the close of 

 the operation a little chlorate of potassa is scattered in 

 the crucible in case the saltpetre happens to contain 

 any sulphates. When cool, it is dissolved in water, 

 and the standard acid added in the manner directed 

 for testing samples of potashes. The number of mea- 

 sures of acid employed is multiplied by 4, in order 

 to obtain the percentage of pure nitre in the specimen. 



In following this method it is impossible to deter- 

 mine the weight of the expelled carbonic acid by 

 means of the apparatus generally employed for this 

 purpose, on account of the large quantity of common 

 salt which has been added. 



The simplest method for the analysis of nitre con- 

 sists in fusing the weighed quantity of nitre with twice 

 its weight of fused bichromate of potassa, until all the 

 nitric acid is driven off. The loss in weight shows 

 the quantity and also amount of pure nitrate of potassa. 



125. GUNPOWDER. 



I. For the estimation of moisture, 5 or 6 grms. of 

 powder are dried over sulphuric acid, or in the air- 

 bath at 100. 



II. A similar quantity of powder is moistened with 

 water, triturated in a mortar, rinsed into a filter, and 

 thoroughly washed. The solution of nitre thus ob- 

 tained is evaporated to dryness in a small weighed 

 porcelain dish, the dry residue heated for some time 

 to 200, or even till the nitre fuses, and its weight 

 determined. 



III. In order to determine the sulphur, 5 grms. of 

 powder are intimately mixed with 5 grms. of anhydrous 



