Chemical Science. 173 



G. On the Contractions ■produced by Heat in Crystals. — M. Mits- 

 cherlich observed* that the mutual inclination of the planes of 

 Iceland spar, varied sensibly by the effect of heat ; and that be- 

 tween 32« and 212« F. the change of the diedral angles at the 

 extremityof the axis of the rhomboid was 8i'. Hence it results, that 

 supposing no dilatation of the crystal perpendicularly to the axis, its 

 cubical dilatation would surpass that of glass by nearly half as much 

 again: but whilst measuring the cubical dilatation of Iceland spar 

 with M. Dulong, M, Mitscherlich found that it was inferior to that of 

 glass, and this leads to the singular consequence that whilst the 

 heat dilates the crystal parallel to its axis, it causes it to contract 

 in a direction perpendicular to it. M. Mitscherlich has assured 

 himself of this fact, by measuring with a spherometer, the thick- 

 ness of a plate of Iceland spar, cut parallel to its axis, at different 

 temperatures. 



It is very probable that sulphate of lime will present an ana- 

 logous effect, but in the inverse direction, i. e., that an elevation of 

 temperature will produce a sensible contraction in the direction of 

 its axis. (A. F.) — An?i. de C/iim. xxvi. 222. 



6. Cyanuret of Iodine. — Proceedings of the Society of Pharmacy 

 at Paris, April 15. M. SeruUas read a memoir on a new com- 

 pound of nitrogen, carbon, and iodine, which he named cyanuret of 

 iodine. This new product is obtained by heating an intimate mix- 

 ture of two parts of cyanuret of mercury and one part of iodine in 

 a small dry retort. When the temperature is sufficiently elevated, a 

 ■white vapour rises, which condenses in the form of light flocculi or 

 small brilliant plates, which are the cyanuret of iodine ; there is 

 produced, at the same time, protiodide of mercury, which remains 

 in the retort. The cyanuret may be purified by a second sublima- 

 tion. This substance has a strong poignant odour, exciting tears ; 

 its taste is very caustic, it does not alter litmus or turmeric paper. 

 Thrown on hot charcoal it evolves violet vapours. It is soluble in 

 water and alcohol. M. Serullas regards it according to his expe- 

 riments, as a compound of 828 of iodine, and 172 of cyanogen. — 

 Jour, de Phar. x. 256. 



See Sir Humphry Davy on this substance. Quarterly Journal, I. 

 p. 289. 



7. Selenium in the Volcanic Rocks of Lipari. — Professor Stromeyer 

 has lately discovered selenium under two different forms, one of 

 which is altogether new. On diluting some faming sulphuric 

 acid, such as is made at Nordhausen from the sulpliatc of 

 iron, he observed that a solid matter separated, and which, on 

 examination, proved to be selenium One pound of the acid gave, 

 on dilution, about a grain of selenium. This substance has 



* See Quarterly Journal, xvii. 157. 



