Mr. Crum on the Analysis of Nitrates, and on Explosive Cotton. 167 



long and thrco-cighths of an inch in diameter; the gases from which are 

 led by a small bent tube mid. ■ tin; receiver in a mercurial trough. 



1 inch at the closed end of the tube is filled with eight grains chlorate of 



potash, ground with chroraate of lead. 

 4 J inches are filled with chromate of lead, among which is ground to powder 



three grains of the gun-cotton. 

 1 J inches contain chromate of lead that has been used to wash out the 



mortar. 

 A glass plug separates these materials from the perforated cork which 

 joins the two tubes. The materials are gradually heated with broad- 

 wicked spirit lamps. Carbonic acid comes over, mixed, when in the 

 receiver, with nitric oxide and the azote of the apparatus ; and when all the 

 gun-cotton is consumed, the lamps are extended to the chlorate of potash. 

 The oxygen gas thus liberated, which in other cases is useful to consume 

 carbonaceous matter that may have escaped the chromate, expels in this 

 case all romains of carbonic acid, and passing itself into the receiver, 

 mixes there with the nitric oxide, and causes its entire absorption by the 

 mercury. Oxygen and azote are then the only gases left along with the 

 carbonic acid, and as those are not absorbable, an addition of half a cubic 

 inch of solution of caustic soda indicates exactly the quantity of carbonic 

 acid present. 



In one experiment, 2*993 grains of gun-cotton (after deducting water 

 and ashes,) yielded 7*952 cubic inches of gas, of which 5733 was carbonic 

 acid, = 0*739 grains carbon, or 



24-69 per cent. 

 A second experiment gave 25*16 



Mean, 24*92 



Elements op Water in Gun-Cotton. — To burn gun-cotton for the 

 purpose of collecting its oxygen and hydrogen in the state of water, I 

 ground up ten grains of it with pounded flint, and used the combustion 

 tube already described, having attached to it a chloride of calcium tube, 

 and afterwards a tube with asbestus moistened with sulphuric acid. 

 But, along with the water, ammonia and other matters were obtained, 

 which destroyed the result. I next used a thin glass tube of a foot 

 and a half long, bent so that a foot in the middle of it could dip into 

 cold water. Such water as would condense at 65° Falir. was collected. 

 The gas was led through it into a mercurial trough, and measured. A 

 trace of cyanogen appeared in the last portions of gas, while the oxygen 

 from the chlorate of potash was burning a quantity of charcoal that had 

 escaped the nitric acid. 



After the experiment, the refrigerating tube was found studded with 

 l.u l'o crystals of bicarbonate of ammonia. It contained very little water in 

 the liquid state. The crystals and the liquid were washed out with more 



Vol. EL— No. 3. 3 



