224 Notices of the Labours of Continental Chemists. 



The oxide is easily freed from the salts of soda by washing. Ac- 

 cording to the methods generally in practice, this preparation 

 is obtained in an impure state, either mixed with metallic an- 

 timony, which is easily detected, or, what is more frequently 

 the case, with the higher oxides. To detect these the author 

 proposes the following method, founded on the well-known 

 fact, that oxide of antimony melts with the sulphuret to form 

 the glass of antimony without any disengagement of sulphurous 

 acid, while the higher oxides are reduced to this protoxide 

 under liberation of sulphurous acid. Fifteen parts of the sup- 

 posed pure oxide are carefully mixed with thirty-five parts of 

 the sulphuret, and the mixture placed in a glass tube, which is 

 connected on the one side by a chloride of calcium tube with a 

 flask for disengaging gas, on the other with a glass tube, which 

 is bent at right angles, and terminates in a small vessel contain- 

 in"- dilute water of ammonia. The mixture is then heated, du- 

 ring which a current of carbonic acid gas is passed over it to 

 prevent any access of air. As soon as the oxide has melted 

 with the sulphuret, the heating is discontinued, and the ammo- 

 niacal liquid subjected to examination. Hydrochloric acid is 

 added to it, and then a clear solution of sulphuretted hydro- 

 gen; the opacity caused by the precipitated sulphur indi- 

 cates sulphurous acid; another portion is treated with dilute 

 sulphuric acid, which must be perfectly free from any oxide of 

 nitrogen, and then a dilute solution of hypermanganic acid, 

 which, when sulphurous acid is present, is instantaneously de- 

 colorated: this is the best test. Only pure oxide, and oxide 

 containing metallic antimony, are easily fusible ; a small ad- 

 dition of antimonious acid renders the fusion difficult ; and 

 with a larger quantity (about 30 per cent.) the mixture can- 

 not be melted over an Argand lamp. — Poggendorff' s Annate?!, 

 liii. p. 161. 



Method of detecting and distinguishing Gum, Dextrin, Grape 

 Sugar, and Cane Sugar. 



M. Trommer has made several experiments to find out a 

 method of distinguishing the above substances in solution ; 

 the method advanced is founded on their different actions to- 

 wards the sulphate of copper when a free alkali is present. 

 Gum solution gives a blue precipitate, which is insoluble in an 

 alkaline liquor, but is soluble in pure water, and can be boiled 

 without becoming black ; a proof that it is not the hydrate of 

 the oxide of copper, but a combination of gum with the oxide 

 of copper. Starch and gum tragacanth exhibit the same ac- 

 tion ; a solution of dextrin affords a deep blue-coloured li- 

 quid, without a trace of a precipitate, which, when heated to 



