524 Royal Society : — 



as it does not dissolve cotton, affords a means of distinguish- 

 ing the two substances. Wlien silk is stirred in a test-glass 

 with the solution by means -of a glass rod, it becomes of a yel- 

 lowish-brown colour, like that of hydrated oxide of iron, gela- 

 tinous, and finally dissolves into a homogeneous solution of a 

 yellowish-brown colour. Sc^utions of the alkalies do not preci- 

 pitate this solution ; sal-ammoniac restores to it its blue colour 

 without precipitating it. By acids the silk is precipitated. Cel- 

 lulose is not at all attacked by the ammoniacal oxide of nickel 

 solution. Starch does not swell up; but inuline is gradually 

 dissolved. 



The same chemist has communicated* some facts in reference 

 to Schweizer's reagent. The solvent property of CuO NH^ is 

 greatly diminished by the pi-esence of salts. The reagent is con- 

 veniently prepared by dissolving fi-eshly precipitated and well 

 washed hydrated oxide of copper in strong ammonia. The 

 richer the solution in oxide of copper, the more rapid is the 

 action ; even the strongest ammonia is without action if it is 

 poor in oxide of copper. The clear filtered solution of cellulose 

 is immediately precipitated by strong solutions of the alkalies : 

 the same is the case, though even more rapidly and completely, 

 with honey, or with a concentrated aqueous solution of gum- 

 arabic or dextrine. Cellulose is undoubtedly contained in the 

 solution as such. Silk is dissolved into a blue solution, its 

 solution in nickel being yellowish bi'own. Salts, solution of 

 sugar, and mucilage precipitate the solution either not at all or 

 very sparingly, and even acids but imperfectly. 



LX. Proceedings of Learned Societies. 



ROYAL SOCIETY. 



[Continued from p. 473.] 

 April 29, 1858. — J. P. Gassiot, Esq., Vice-President, iu the Chair. 



THE following communications were read : — 

 "An Account of the Weather in various localities during the 

 15th of March, 1858 (the dav of the Great Solar Eclipse). By Ed- 

 ward Joseph Lowe, Esq., F.R.A.S., F.G.S., F.L.S., F.Z.S. &c. 



"On the Structure and Functions of the Hairs of the Crustacea." 

 By Campbell De Morgan, Esq. 



" Note on the Measurement of Gases in Analysis." By A. W. 

 Williamson, Ph.D., F.R.S., Professor of Chemistry iu University 

 College, and W. J. Russell, Ph.D. 



In Bunsen's admirable method of gas analysis, considerable time 

 * Liebig's Annalen, July 1868. 



