Miscellanies. 373 



when pure ; but, however small the quantity of sulphate or muriate, 

 it may contain, it is rendered turbid by the addition of barytic or 

 silver salts. — Bui. de Mulh. No. 6« v. 58. 



Use of 



As mica 



is not fragile, and does not change in the flame of a taper, it may 



be employed with much advantage, as a support to substances which 



we wish to expose simply to the flame of a lamp or candle ; take a 



thin plate of mica, which may be easily separated from the mass by 



a knife, and after each experiment, wipe it with a moist cloth. — Arch, 

 de Brandes. 



8. Changes of volume on a mixture of alcohol and water, by F*. 

 Rudberg. — The maximum of contraction is 3.775 per cent, of the 

 mixture, and this takes place in a mixture containing 0.53929 of ab- 

 solute alcohol — the rest water ; and it is composed of 3 atoms of 

 water and 1 atom of alcohol. The lower the temperature, the 

 greater the contraction. — Ann. de Chim. t. 48, p. 33. 



9. Indelible coloring. — In impregnating, in an even manner, the 

 surface of cloth with a solution of nitrate of silver, and after drying 

 it, immersing the cloth in a solution of hydrochlorate, of of chloride 

 of lime, chloride of silver is formed, which adheres strongly to the 

 fibre, and if afterwards the cloth is exposed to the light, it immedi- 

 ately acquires a bluish gray tint, very clear and agreeable, which re-* 

 sists the action of chlorine, ammonia, &e. In order that it may be 

 perfectly uniform, the whole piece must receive the action of the 

 sun's rays at the same time. — M. Rolriquet, Jour, de Pharm. 



10. Artificial ultramarine at a moderate price. — Since M. Tas- 

 saert made the curious observation of the blue color of soda furna- 

 ces, and Vauquelin proved the identity of this coloring matter with 

 that of lapis lazuli, the hope has been cherished that, sooner or later, 

 ultramarine would be manufactured in sufficient abundance. The 

 Society of Encouragement having offered a premium on this subject, 

 M. Guimet presented a beautiful blue of an azure reflection, and the 

 premium was adjudged to him. M. Robiquet, who bad also engaged 

 in this research, thought it right to publish the process which had suc- 

 ceeded best with him, and which, without giving so beautiful a blue 

 as that of Guimet, will nevertheless furnish the color at a lower price,, 

 and applicable to paper staining. 



Vol. XXIV.— No. 2. 48 



