SCIENTIFIC SUMMARY. 
187 
yellow or greenish-yellow colour, decomposable with deflagration. The 
graphitic oxide may be decomposed, as will be shown, in such a way as to 
cause the disappearance of the whole of the carbon. 3rd. In a mixture of 
diamond, graphite, and amorphous carbon, the amorphous carbon is entirely 
dissolved, leaving a mixture of graphitic oxide and diamond. This cannot 
be dissolved by solvents, but the diamond may be isolated as follows : Dry 
the mixture ; then heat in a tube closed at one end. The graphitic oxide is 
destroyed, leaving pyrographitic oxide. This, reoxidised by chlorate of 
potash and nitric acid, forms soluble products, and a proportion of graphitic 
oxide much smaller than that first destroyed. On decomposing this new 
graphitic oxide by heat, and then reoxidising the new pyrographitic oxide, 
only traces of graphitic oxide will be discovered. After three or four 
operations the whole of the graphitic oxide will disappear, leaving only 
the diamond. 
Detection of Mercury in Cases of Poisoning. — This is a point of much 
importance to medical men and to professional toxicologists. The following 
method was recently employed by M. Buchner in a case of poisoning 
with corrosive sublimate. The organic remains having been disintegrated by 
a hot mixture of chlorate of potash and hydrochloric acid, the solution was 
diluted and saturated with sulphuretted hydrogen. After the lapse of some 
hours, the sulphide formed was collected, dissolved in aqua regia, and 
reduced by evaporation to a small volume. A little water being added, a 
bright piece of copper wire is placed in the liquid ; and when mercury is 
present the wire becomes grey, at the latest, in two days. The copper is 
withdrawn, dried between folds of blotting-paper, and heated in a wide test 
tube. The mercury is more easily distinguished by removing the wire^ 
and placing in the tube a drop of tincture of iodine. M. Eiederer, having 
remarked that the sulphide of mercury which is formed by this process 
always contains organic matter, has recourse to dialysis. He operates in the 
following manner. After disorganisation by chlorate of potash and hydro- 
chloric acid, the mercury in solution is precipitated by sulphuretted hydrogen, 
the sulphide collected dissolved in a mixture of chlorate of potash and 
hydrochloric acid, and dialysed with 500 c.c. of water. At the end of five 
days, the water is evaporated and the dialysis repeated. After this treat- 
ment, the solution is again saturated with sulphuretted hydrogen ; the 
precipitate is washed with ammonia and sulphide of ammonium, then with 
weak nitric acid, and finally treated afresh with hydrochloric acid and 
chlorate of potash. Operating upon dogs with calomel, M. Eiederer has 
recognised that the greater part of the mercurial compound is eliminated by 
the excrements, and that, for the rest, more collects in the liver than .in the 
muscles. — Paris correspondent of Chemical Neivs, January loth. 
JIo 2 v to prepare Nitrogen. — According to a recent number of Cosinos, a new 
method for this purpose has been devised by Signor Levy. He heats bichro- 
mate of ammonia, by which means he changes it into green sesquioxide of 
chromium, with evolution of water and nitrogen. 
Action of Sulphate of Alumina on Turbid Water . — The Photographic 
News, quoting the Technologist, states, what is already well known to 
chemists, that, whatever be the nature and quantity of the earthy 
substances held in suspension in turbid water, it becomes fit to drink 
