the Halogens, Nitrogen, Sulphur and Oxygen. 365 



My analysis of the lampblack gave 1 per cent of hydrogen, 

 - 6i of ash and in an air-dry portion 0*23 per cent of nitrogen 

 by the absolute method. After igniting for two hours in dry 

 nitrogen and allowing to cool in the gas, no nitrogen was ob- 

 tained on burning with oxide of copper. This kind of lamp- 

 black when pressed into compact pieces conducts electricity, 

 and when heated in vacuo it yields a small sublimate as ob- 

 served by Mallet. 



The gas carbon used was from the inner portion of a thick 

 piece. A combustion of 1 # 742 gram of it yielded - 035 per 

 cent of hydrogen and - 88 of ash. 



The chlorine used in the experiments was made from salt, 

 manganese dioxide and sulphuric acid, and was passed through 

 one wash-bottle containing water and one containing oil of 

 vitriol. The temperature in the experiments was the highest 

 attainable in a gas combustion-furnace, that is, a bright red 

 heat. A hard glass or porcelain tube was used to hold the 

 charcoal during the ignition in chlorine. 



Experiment 1. — 10 grains of sugar charcoal were ignited in 

 chlorine for three hours, then left for a day over solid caustic 

 potash, and finally heated to redness for an hour in vacuo. 

 The product weighed 10*304: grams and contained 3*7 per cent 

 of chlorine.* 



Another portion of 10 grams of the same charcoal was exposed 

 at common temperature to a current of chlorine for three hours, 

 then dry air was passed through the tube for 15 minutes. The 

 gain in weight of the charcoal was 0'098 gram which was not 

 diminished by exhausting the tube and then opening to the 

 air. The results show that cold dense sugar charcoal takes up 

 much less chlorine than when heated. Probably chlorine is 

 simply occluded by cold charcoal ; whether chlorine is chem- 

 ically combined which is retained by hot charcoal will be dis- 

 cussed after the experimental results are given. 



Experiment 2. — Sugar charcoal was heated to redness in a 

 porcelain tube, then chlorine was passed through the tube for 

 three hours, and while red hot the chlorine gas was displaced by 

 nitrogen. The charcoal as it came from the warm tube gave 

 off no chlorine, of which it was found to contain 4*6 per cent. 



Experiment 3. — (a) Chlorine was passed for two hours over 

 cold lampblack, and then (b) over glowing lampblack. Both 

 preparations of chlorinated lampblack were left for a day 

 over solid potash in a partial vacuum. 7 - 9 per cent of chlorine 



* The estimation was made by burning the chlorinated charcoal in moist oxygen 

 and passing the products of combustion through dilute ammonia to absorb the 

 chlorine, which was afterwards precipitated as silver chloride by the addition of 

 silver nitrate and nitric acid It was found that chlorinated charcoal or lamp- 

 black burned with difficulty and often incompletely in dry oxygen. 



