204 



Mr. J. Spiller on New Sources 



[Mar. 6, 



and while the mercury-rap ours are still streaming out, an iron test-tube, 

 previously prepared with great care and charged with 4-5 grms. of 

 potassium, is dropped into the bottle, the neck reinserted, and after the 

 u'Jwle of the bottle has been immersed into the zinc, the blast of the forge 

 is forcibly increased so as, in the shortest possible time, to bring the zinc 

 into the state of boiling, proper arrangements being made for keeping 

 the neck of the bottle red-hot. The potassium in a short time begins to 

 volatilize, issuing in jets into the air and depositing caustic potash at 

 the nozzle, which must be kept clear' by means of an iron wire, As 

 soon as the distillation of the potassium ceases, the nozzle is closed by 

 means of a ground-in wire plug, at once immersed into a mass of mer- 

 cury contained in a test-tube, and the bottle withdrawn to a proper 

 support, on which it is allowed to cool. 



After it has reached a manageable temperature, the bottle is inserted 

 into a mass of recently boiled water, the wire plug withdrawn, and the 

 hydrogen formed by the action of the water on the potassium pumped 

 out, by means of a " Sprengel," into a eudiometer, to be measured. 



In the experiments we have hitherto carried out, we have satisfied 

 ourselves that the amount of mercury-vapour not swept out by the potas- 

 sium is quite inappreciable ; and as our object has been in the mean time 

 to merely arrive at approximate results and to perfect our methods of 

 manipulation, we have neglected the minute correction, which, on 

 account of that small remnant of mercury, ought, strictly speaking, to 

 have been applied to the volume of the vapour as calculated from the 

 capacity of the bottle in the cold, the coefficient of expansion of iron, and 

 the temperature (1040° Deville) at which the vapour was measured. 



The results of our observations conclusively show that the density of 

 potassium-vapour, as produced in the process described, cannot exceed 

 45 times that of hydrogen, and that therefore the molecule of potassium 

 consists of two atoms (K 2 ). 



We intend to prosecute our research in other directions, proposing to 

 ascertain, if possible, the densities of the iodides of caesium, rubidium, 

 and potassium, these being, according to Bunsens experiments, the most 

 volatile of the haloids of the alkali metals. 



II. " On New Sources of Ethyl- and Methyl-Aniline." By John 

 Spiller, F.C.S. Communicated by Dr. Debus, F.R.S. Re- 

 ceived December 10, 1872. 



In the process of manufacturing the Hofmann violet by the action of 

 etlrylic or methylic iodide upon rosaniline or one of its salts, there is al- 

 ways produced a considerable quantity of a dark-coloured resinous or pitch- 

 like substance, which has received the name of " Hofmann gum." This 

 by-product varies in amount and consistence according to the shade of 

 violet simultaneously produced being much more abundant when the 



