1826] Scientific Notices — Chemistri/, 46'1 



are very fine, and still more when they are soluble in the ordi- 

 nary menstrua, it is sometimes impossible to clear them;, 

 although perfectly pure, by any other method than repeated 

 crystallization and digestion with animal charcoal ; both of 

 which processes are troublesome, and occasion considerable 

 loss. M. Robinet has proposed a new and very simple method, 

 which was suggested to him, in consequence of observing, that 

 when a parcel of crystals came into contact with the mouth of 

 the pipette during the act of suction, they were instantly and 

 perfectly cleaned. The process depends on the transmission of 

 a current of air through the crystals. He has suggested various 

 forms of apparatus for the purpose. The simplest consists of a 

 double-mouthed bottle, with a funnel in one mouth, and a bent 

 tube in the other ; the lower opening of the funnel being 

 obstructed by a ball of cotton-wool, and the crystals placed 

 above the cotton. On sucking the air through the crystals by 

 a bent tube, they are cleaned in a few seconds ; and, if necessary^ 

 the operation may be repeated after previously introducing a 

 little water into the funnel. A convenient way of constructing 

 the apparatus so as to work of itself, is to make the second tube 

 reach the bottom of the bottle with one limb, and with the other 

 a vessel of water situated on a lower level. The whole bottle 

 and tube being filled with water, the funnel is to be introduced, 

 and the water then allowed to run off by the syphon. On the 

 large scale a more suitable apparatus will be a tube from a 

 steam-boiler, by which the bottle may be filled with steam from 

 time to time. 



The steam communication being shut ofi", and the steam in 

 the bottle condensed, the stream of air will immediately carry 

 through with it the whole of the mother-water from the most 

 silky crystals. — (Journal de Chimie Medicale.) 



2. On the Decomposition of Cyanate of Silver, by Sulphuretted 

 Hydrogen. By Dr. Liebig. 



M. Gay Lussac and I have already shown, observes Dr. 

 Liebig, that sulphuretted hydrogen decomposes cyanate of sil- 

 ver ; the cyanic acid is not, however, separated in a pure state ; 

 one part of it combines with the sulphuretted hydrogen, and 

 pecuHar compounds are formed which have in general the cha- 

 racters of acids. When cyanate of silver is decomposed by 

 bydriodic and muriatic acid, hydrocyanic acid is evolved, and 

 new acids are obtained which contain iodine and chlorine, and 

 which have the property of giving deep red coloured solutions 

 with the salts of peroxide of iron, after having been neutralized 

 with a base. With sulphuretted hydrogen no hydrocyanic acid 

 is obtained, and the new acid immediately produces a deep red 

 coloured fluid with the persalts of iron, without previous neu- 

 tralization with a base. 



