the Halogens, Nitrogen, Sulphur and Oxygen. 373 



inately mixed with freshly ignited copper oxide were placed in 

 a combustion tube, and then copper oxide, a long roll of bright 

 copper gauze and hydrogen sodium carbonate were put in. 

 The tube was exhausted by a mercury pump and the combus- 

 tion was made as usual in the absolute method. O2 C0 of gas 

 was collected, the amount repeatedly obtained in blank tests. 

 This method was employed in all the estimations of nitrogen 

 in charcoal, experience having shown that it is difficult to 

 burn charcoal with copper oxide alone, and that it is better to 

 mix the coal with 5 parts of chlorate than to place the latter 

 in the end of the tube. In none of the determinations of 

 nitrogen was the copper gauze perceptibly oxidized. 



Experiment 16. — Uric acid was heated in a covered platinum 

 crucible over a large gas burner as long as combustible gases 

 came off. The resulting charcoal contained 34 - 06 per cent of 

 nitrogen. 



Experiment 17. — Uric acid was charred by heating gradually 

 at first, then for half an hour to the highest temperature of a 

 Perrot furnace. The charcoal after this intense ignition 

 yielded 3 "52 per cent of nitrogen. 



Experiment 18. — Uric acid contained in a covered platinum 

 crucible was heated gradually and the charcoal formed was 

 kept at a dull ret heat for 15 minutes after the escaping gases 

 ceased to burn. This product had 39*62 per cent of nitrogen. 

 It was an exceedingly bulky black powder which gave off 

 ammonium cyanide when heated in a current of dry hydrogen. 



Experiment 19. — 1 gram of paracyanogen left 6 milligrams 

 of black residue after heating for two minutes in a covered 

 platinum crucible over the same lamp that was used in 16. 



Nitrogenous charcoal which has been intensely heated does 

 not contain paracyanogen as this is converted into gaseous 

 cyanogen by heat. It is possible that the charcoal from uric 

 acid with the large content of nitrogen is composed in part of 

 paracyanogen. 



Charcoal containing Sulphur. 



Berzelius* made the following statement regarding a solid 

 sulphide of carbon : " Die Kohle, welche zur Darstellung dieser 

 Yerbin dung (carbon disulphide) angewandt worden ist, enthalt 

 Schwefel in chemischer Verbindung, der nicht durch Gliihen 

 ausgetrieben werden kann, wenn dabei der Zutritt der Luft 

 verhindert wird." This fact, not mentioned in recent works on 

 chemistry, must be familiar to manufacturers of carbon disul- 



*Lehrbucli der Chemie, 1843, i, 300. 



