PROFESSOR H. B. DIXON ON THE RATE OF EXPLOSION IN GASES. 
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with strong alcoholic potash and finally with oil of vitriol. The generating flask (of 
2 litres capacity) was kept at 30° C. 
An analysis of the gas by explosion with air in McLeod’s gas apparatus showed 
99'3 per cent, of marsh gas. 
Ethylene. —The ethylene was prepared by the method given by Erlenmeyer and 
Bunte. 25 grms. of absolute alcohol are mixed with 150 grms. of pure sulphuric 
acid, and the mixture is heated in a large flask, on a sand bath, to 160°-170° C. A 
mixture of one part alcohol and two parts sulphuric acid is then slowly added by a 
tap-funnel. Great difficulty was experienced in getting rid of all acid gases from the 
ethylene. The gas was passed (1) through two wash-bottles containing oil of vitriol, 
(2) through a tower packed with pieces of solid potash, (3) through two wash-bottles 
containing strong potash solution, (4) through a second tower packed with pieces of 
solid potash. The large quantity of air contained in the flask and washing apparatus 
rendered it difficult to obtain the gas quite free from air. The gas was analysed 
and found to be free from sulphurous acid, but it contained small quantities of 
nitrogen. Allowance was made for the presence of this diluent gas in making up 
the mixtures of ethylene with oxygen, &c. The percentage impurity in the ethylene 
could be reduced to 1 per cent.; no other gas used In these experiments presented 
the same difficulty in making pure. 
Acetylene. —The acetylene was prepared by the action of strong alcoholic potash or 
ethylene dibromide. The potash was dissolved in amyl alcohol. The gas evolved from 
the boiling solution was passed through a second flask containing boiling potash 
solution, and then into an ammoniacal solution of cuprous chloride. The precipitated 
cuprous acetylide was washed with dilute ammonia solution and kept till required under 
this solution. On warming the red precipitate with strong hydrochloric acid to 50° C. 
a regular stream of acetylene was given off. It was washed with water, dried with 
caustic potash, and collected over mercury. Analysis showed that the gas was pure. 
Ammonia .—The ammonia was distilled from a strong aqueous solution, wms dried 
by caustic potash, and was collected over mercury. 
Carbonic Oxide .—This gas was prepared by gently warming formic acid with pure 
sulphuric acid diluted with an equal volume of water. It was washed with potash 
solution. 
Cyanogen. —Ile-crystallised mercuric cyanide was powdered and carefully heated to 
drive off moisture. The dry pov/der was introduced into a steel retort with a long 
neck. After a considerable quantity of cyanogen had been allowed to escape, the 
gas was collected directly in a mercury holder. The retort was raised to dull redness 
in a fireclay furnace, heated by gas. 
Oxygen. —The oxygen was prepared by heating powdered chlorate of potash in a 
hard glass flask. It was washed by a solution of caustic potash. 
Nitrons Oxide. —This gas was prepared by heating pure ammonium nitrate in a 
