158 Intelligence and Miscillancotts Articles, 



ARTIFICIAL FORMATION OF CRYSTALLIZED IRON PYRITES. 



This process of M. Wohler consists in slowly heating in a glass 

 flask, or other convenient vessel, peroxide of iron, sulphur, and hy- 

 drochlorate of ammonia, intimately nnxed, until all the ammoniacal 

 salt is sublimed, suffering the mass to cool slowly, and afterwards 

 washing with water ; there will be found at the bottom of the vessel 

 heavy octohedra and tetrahedra, of a yellow colour, which are iden- 

 tical with the conimon crystallized pyrites. The larger the mai^s of 

 the materials employed, the larger and more perfect are the crystals 

 obtaine<l. — Jour, de Pharmacie, Oct., 1836. 



ON THE DEGREE OF COLD PRODUCED BY SOLID CARBONIC 



ACID. 



M. Thilorier has invented an apparatus of a very simple con- 

 struction, (which, however, we regret to say, is not described,) by 

 which raas'Cs of from two to three hundred grains of solid carbonic 

 acid can be quickly and oecononiically obtained. 



The acid obtained by this apparatus resembles compact snow. In 

 his former experiment on the degree of cold produced by this sub- 

 stance, the author directed a jet of liquid carbonic acid on the bulb 

 of a thermometer, &c., but the facility with which the solid acid is 

 now obtained in abundance has allowed M. Thilorier to use a pre- 

 ferable method of manipulation. The bulb of a thermometer was 

 placed in the midst of a small portion of solid carbonic acid, and at 

 the expiration of about two minutes the thermometrical index be- 

 came stationary, having sunk to — 162° Falir. A few drops of aether 

 or alcohol poured on the solid acid do not indicate any appreciable 

 alteration o^ temperature. The aether forms a half liquid mixture 

 of about the consistence of melting snow ; but the alcohol, uniting 

 with the solid acid, congeals, forming a hard, brilliant and semi- 

 transparent ice. This congelation of anhydrous alcohol does not 

 occur unlej^s it is mixed with the acid, for when the alcohol is 

 poured into a silver tube, and this plunged into solid carbonic acid, 

 no change is produced. 



The mixture of alcohol and solid carbonic acid begins to melt at 

 — 153° Fahr., and, commencing at this point, the temperature docs 

 not vary ; thus affording at this extremity of the thermometric scale 

 a point as invariably fixed as that indicated by melting ice. 



When 1.30 or 180 grains of mercury are placed on a small and 

 concave portion of solid carbonic acid, it solidifies in the course of 

 a iew seconds, and continues so as long as any solid carbonic acid 

 remains, that is, fur 20 or 30 minutes, when the weight of the acid is 

 about 110 grains. 



Although the addition of aether or alcohol does not increase the 

 degree of cold, yet it enables the solid acid to moisten, and to ad- 

 here more closely to, the surfaces of bodies, thus greatly increasing 

 its refrigerating power. A portion of carbonic acid, on the addition 

 of a fQw drops of alcohol or aether, will solidify from 15 to 20 times 

 its weight of mercury, thus affording an easy and elegant method, far 

 superior to any ycl used; for ihc solidification of mercury. 



