520 REPORT—1868. 
was added at intervals during a fortnight, so that altogether it amounted to 
about five per cent. of the hquid. 
I have passed cyanogen and hydrogen, both perfectly dry, over platinum- 
black heated to 130°C. The tube containing the platinum was not connected 
till the hydrogen had been passed for about half an hour through the appa- 
ratus and drying tubes, and till the cyanogen was given off freely. ‘The 
hydrogen was dried by passing over five feet of pumice-stone soaked with 
sulphuric acid. The two gases were mixed in a three-necked Woulfe’s bottle, 
before passing over the platinum. They next passed into an empty bulb 
apparatus, and then into dilute acid (HCl). On making the connections, 
dense fumes filled that part of the apparatus next theacid. After some time 
a small quantity of liquid condensed in the empty bulb apparatus next the 
platinum. This was found to be strongly alkaline, and was neutralized with 
hydrochloric acid, and filtered repeatedly from a brown deposit which sepa- 
rated on standing. The determination of the platinum in the platinum-salt 
gave a result corresponding pretty closely to that which would be given by 
the platinum-salts of ethylenediamine or methylamine. The quantity of 
 platinum-salt (a little over a decigramme) was, however, too small to give a 
sufficiently reliable percentage. The platinum-black soon changes, and loses 
its power. Water then gives with it a very dark-coloured solution, which I 
have not much examined. 
In order to obtain perfectly definite results in the hydrogenation of cyanogen 
and other cyanides, I have recently adopted the plan of estimating the amount 
of metal dissolved, and of the hydrogen or other gases evolved, from perfectly 
known quantities of materials, making each experiment as perfectly quanti- 
tative as possible. The experiments which I have made, and those which I 
am now carrying on, make me confident of being soon able to clear up the 
difficulties which I have worked at so long unsuccessfully. 
Note on the Solubility of Cyanogen in Sulphuric Acid.—Cyanogen dissolves 
readily in strong sulphuric acid, and is evolved in great measure unchanged 
on addition of water. The solution of cyanogen in sulphuric acid produces 
a beautiful purple colour with cuprous cyanide. 
Note on the preparation of Olefiant Gas.—Wohler recommended to add 
sand to the mixture of sulphuric acid and alcohol to prevent frothing. The 
objection to this is that the flasks used are very apt to break, by a part of 
the bottom becoming dry, and the liquid afterwards running down on it. I 
have found that pumice-stone in small pieces prevents frothing equally well, 
or better, and since it floats on the liquid, there is much less risk of breakage. 
