314« Intelligence and Miscellaneous Articles, 



the bichloride is to be found in the filtered liquor : and at first it 

 would be quite natural to suppose that reduction had occurred, and 

 that protochloride of mercury would be found insoluble in the filter ; 

 it is however readily shown that this is not the case, as was proved, 

 according to M. Esprit, by the following experiment : — a solution 

 was made of 1 grm. of sublimate in 100 grms. of distilled water, 

 and this solution was treated with 20 grms. of well- washed animal 

 charcoal : the liquor, treated with potash, hydrosulphate of ammonia 

 and iodide of potassium, did not indicate the presence of a mercu- 

 rial salt ; but on washing the charcoal which had been used in the 

 experiment with a mixture of alcohol and aether, sublimate was 

 rapidly dissolved ; and in so large quantity, that when a tube was 

 dipped into the solution, it gave a very distinct red precipitate with 

 a solution of iodide of potassium. 



This experiment, which the author repeated several times, and 

 always with the same success, induced him to think that carbon does 

 not act upon metallic solutions merely as a reducing agent, nor does 

 he attribute it to the mere porosity of the charcoal, but he supposes 

 that the metallic salt is retained by a peculiar force or special affinity. 

 In studying the action of charcoal on metallic solutions, it is requi- 

 site to employ it quite free from sulphurets and calcareous salts, the 

 presence of which complicates the operation, and does not allow of 

 a proper estimate of the peculiar action of the charcoal. — Journ. de 

 Chim. Med., Septembre 1850. 



ON THE COPPER TEST FOR SUGAR. BY M. LASSAIGNE. 



It has been long known, according to the experiments of M. 

 Frommherz, that tartrate of copper dissolved in a solution of potash 

 is easily reduced when heated with glucose, and converted into sub- 

 oxide of copper. The same author has stated that cane-sugar, which 

 differs in composition from glucose, does not act upon this reagent. 

 It is on these facts that M. Barreswil has founded his process for 

 estimating the quantity of sugar. 



The employment of this reagent is even indicated, in several recent 

 chemical works, as capable of distinguishing between cane-sugar and 

 glucose. 



The alkaline solution of copper, employed as a test liquor, is pre- 

 pared by two published methods ; one by M. Barreswil, and the 

 other by M. Poggiale. The first consists in dissolving with heat, in 

 one-third of a litre of distilled water, 50 grammes of bitartrate of 

 potash, and 40 grammes of carbonate of soda, and afterwards adding 

 30 grammes of powdered crystallized sulphate of copper ; after boil- 

 ing, allow the solution to cool, and lastly add 40 grammes of potash 

 dissolved in one-fourth of a litre of water ; it is made up a litre and 

 again boiled. The second method, proposed by M. Poggiale to de- 

 termine the presence of sugar of milk, which also reduces the oxide 

 of copper, like glucose, consists in dissolving in 200 grammes of 

 water 10 grammes of crystalline sulphate of copper, 10 grammes or 



