CHEMISTRY. 225 



is added cream of tartar, ciystallized protochloride of tin, and 

 some lumps of pure metallic tin. The author states that, instead 

 of this mixture, he uses, with very good success, a solution of one 

 part of protochloride of tin in 10 parts of water, to which he 

 next adds a solution of two parts of caustic soda in 20 parts of 

 water; the mixture becomes turbid, but this does not affect the 

 tinning operation, which is effected by heating the objects to be 

 tinned in this fluid, care being taken, at the same time, to j^lace 

 in the liquid a piece of perforated block-tin jDlate, and to stir up 

 the fluid during tlie tinning with a rod of zinc. — Dr. HilUer^ in 

 the Moniteur Scientijique. 



Silvering Cast Iron. — M. Bbttger recommends the use of a 

 bath prepared in the following manner : 15 grams of nitrate of 

 silver are dissolved in 250 grams of water, and 30 grams of cyan- 

 ide of potassium are added ; when the solution is complete, the 

 liquid is poured into 750 grams of water wlierein 15 grams of 

 common salt have been previously dissolved. The cast iron in- 

 tended to be silvered by this solution should, after having been 

 well cleaned, be placed for a few minutes in a bath of nitric acid 

 of 1.2 sj), gr., just previous to being placed in the silvering 

 fluid. — Dniggists' Circ. 



Adulteration of Sulphuric Acid. — {Rev. Hebd. de Chim.) — It 

 appears that some Continental makers of this acid are in the habit 

 of adding to ordinary chamber acid a sufficient quantity of some 

 cheap acid sulphate, so as to bring the sulpliuric acid, as far as 

 hydrometrical tests are concerned, up to the desired degree of 

 density. M. Fleischer, having cause to complain about the bad 

 quality of indigo-carmine prepared with a certain sample of sul- 

 l^huric acid, was induced to evaporate some of the acid, and on 

 doing so discovered the formation of cr3'stals of sulphate of soda. 

 This kind of adulteration, however readily detected, might cause 

 in many dye and madder and garancine works very serious loss 

 and great inconvenience, and is a gross fraud ; the inducement is 

 the saving of the cost of evaporation and apparatus connected 

 therewith. — Ch. Neios. 



Metallic Uranium. — Dr. Bolton has succeeded in preparing 

 uranium by reducing the double fluoride of uranium and potas- 

 sium by means of sodium. The double salt is prepared from the 

 oxyfluoride by exposure to sunlight in the presence of an or- 

 ganic acid. It falls down as a beautiful green powder. This 

 })OAvder is mixed with proper equivalents of sodium and anhy- 

 drous chloride of potassium, and is fused in a porcelain crucible 

 inclosed in a Hessian crucible lined with charcoal. The heat re- 

 quired at first is moderate, but, as soc<!i as the reduction is accom- 

 plished, must be rapidly I'aised to pievent oxidation and loss of 

 the metal. This melhod is analogous to the preparation of alu- 

 minum from cryolite, and appears to have been perfectly successful 

 in the hands of Dr. Bolton. — Jour, of App. Chem. 



Tungstate of Barium is said to form an excellent white paint, 

 which has as good a tone and depth as white lead, and is not 

 blackened by exposure to atmospheric influences. 



Luting. — Prof. Hirzel, of Leipsic, reconmiends as a lute for 



