1G4 Mr. Crum on the Analysis of Nitrates, and on Explosive Cotton. 



composition, and easily obtained in a state of purity, — to which I hart 

 recourse as a means of proving the accuracy of the method, and detecting 

 any fallacy to which it might be liable. 



Nitric Acid in Nitrate of Potash. — The salt I employed was purified 

 by repeated crystallization, and fused at little more than its melting heat. 

 A glass jar, eight inches long and an inch and a quarter in diameter, is 

 filled with, and inverted over mercury. A single lump of the fused nitrate, 

 weighing about six grains, is let up into it, and afterwards fifty grains of 

 water. As soon as the nitrate is dissolved, 125 grains of sulphuric acid, 

 ascertained to be free from nitric acid, are added. By the action of the 

 mercury upon the liberated nitric acid, deutoxide of nitrogen soon begins 

 to be evolved, and usually in about two hours, without the application of 

 heat, the whole of the nitric acid is converted into that gas. Occasional 

 agitation is necessary, and it is easily performed by giving a jerking 

 horizontal motion to the upper part of the jar. The surface of the 

 sulphuric acid is then marked, and three-fourths of a cubic inch of solution 

 of sulphate of iron, recently boiled, let up into the jar. The gas is 

 rapidly absorbed, except a small portion at last, which must be left several 

 hours to the action of the solution, or be well agitated in a smaller tube 

 with a fresh portion of it. No correction of the nitric oxide has to be 

 made for moisture; for the mixture of acid and water which I employed, 

 as I ascertained by direct experiment, has no perceptible force of vapour. 

 In one experiment, 



5*40 grains nitrate of potash yielded 



4*975 cubic inches of gas, at 60° Fahr., and bar. 30 inches. 



The residue not absorbable by sulphate of iron, was 

 0015 cubic inch; leaving 

 4*96 cubic inches of nitric oxide, =1*594 grains N0 2 , and which 



correspond to 

 2*869 grains nitric acid, or 53*13 per cent, of the nitrate of potash. 



Four consecutive experiments made in this manner yielded — 



5313 

 5314 

 53*73 

 53*29 



Mean, 53*32 

 Or leaving out the third experiment — 



53*19 

 The calculated per centage of nitric acid in nitrate of potash, the acid 

 being represented by 6*75, and the potash by 5*8992, is — 



53*36* 

 In order further to determine whether the presence of organic matter 



* By Thomson's numbers, the per centage of nitric acid in nitre is 52*94. By Berzelius, 

 •>3-44. 



