Chemical Science. 225 



very strong heat. The heated mass is to be dissolved in mu- 

 riatic acid, and the solution evaporated to dryness, in order to 

 separate the silica. Sulphuric acid is afterwards added, and 

 the mass is heated till the greater part of the muriatic acid is 

 driven ofF. The residue is next diluted with water, and the li- 

 quid separated from the gypsum by strong expression. The 

 solution obtained is then digested with carbonate of lime, in or- 

 der to precipitate the alumine, and afterwards filtered and eva- 

 porated. The crystals of sulphate of lithia are then easily sepa- 

 rated from the remaining sulphate of lime. If it is desired to 

 prepare the lithia in the state of carbonate, the sulphate is 

 to be decomposed by acetate of barytes, or of lead, and 

 the acetate of lithia obtained decomposed by heat, and the 

 carbonate separated by solution, Sec. — Edin. Phil. Journ. vi 

 p. 12. 



2. [Preparation of Ef Mop's 3Iineral.—DT. Taddei recommends 

 the following process for the preparation of this substance, as 

 being one which effects the combination immediately, and in a 

 more perfect manner than that generally employed. Put one 

 part of sulphuret of potash into a mortar, witli three or four 

 parts of running mercury ; triturate together, adding a little 

 water by degrees, until the whole is reduced to a homogeneous 

 black paste ; then add flowers of sulphur, in equal quantity 

 to the mercury employed, and mix the whole by a short tritu- 

 ration. Then wash the whole ; and filter with repeated por- 

 tions of water, till all the alkaline sulphuret is removed. 



Ethiops thus prepared is not of the black colour of that ob- 

 tained by simple trituration, but it is a more perfect combi- 

 nation. Dr. Taddei says, that the addition of a little sul- 

 phuret of potassa to the mixture of sulphur and mercury, does 

 not do away with a long trituration, but that, proceeding as 

 above, the substance is prepared instantly.- Giomule di Fisica, 

 iv. 12. 



3. Preparation of Arseniuretted Hydrorjen. — M. Serrulas, in 

 his highly interesting Memoirs on the Alloys of Potassium, gives 

 the following process for the preparation of arseniuretted hy- 

 drogen. It depends on the action of water on the triple alloy 

 of arsenic potassium and antimony. For this purpose a mix- 

 ture must be made of two parts' of antimony, two parts of 

 cream of tartar, and one part of oxide of arsenic, they must be 

 well triturated together in a mortar, and heated strongly for 

 two hours in a close crucible. The alloy which results when 

 in contact with water, produces hydrogen gas saturated with 

 arsenic, and it may be preserved for any length of time in 

 closed vessels. For an experiment or lecture, 8 or 10 grammes, 

 (123 to 1.54 grains,) reduced to a coarse powder, are to be 



Vol. XIII. Q 



