Scientific Intelligence. 279 





i 



SCIENTIFIC INTELLIGENCE. 



I. Chemisthy and Physics. 



1. Crystalline form of the Rhomhohedral Metals, (Berichte der 

 Ben. Akad.)- — Prof. G. Kose, In continuation of his previous investi- 

 gations, has examined an artificial crystal of Tellurium obtained by 

 Mitscherjich. The form was a regular six-sided prism terminated by 

 rhomhohedral faces. The angle of the rhombohedron at the terminal 

 edges was found to be 71° 51'. This rhombohedron is therefore a secon- 

 dary to the primary rhombohedron. Prof. Kose also reckons among the 

 rhomhohedral metals the Tetradymile (Tellurvvismuth) from Schemnitz. 

 It affords the two rhombohedrons 81^ 2' and 66° 40' according to Hai- 

 dinger, the former being that, parallel to whose faces, composition occurs 

 and twins are formed. Prof. Rose is therefore inclined lo consider ihig 

 j^ineral as a joint crystallization of the three constituents, bismuth, tel- 

 lurium and sulphur, rather than a chemical compound. Zinc is also 

 included among the rhomhohedral metals, No^gerath has observed it 

 in hexagonal prisms and this is confirmed by Rose. The latter found 

 %,. lor the inclination of the base on three adjacent planes replacing the 



basaj edges respectively 110^ 35^—110° 4*0', 110^ 31'— 110° 42', and 

 111° 45' — 111° 50', The discrepancy is considered not more than 

 was !o be expected from the character of the crystal, and the prism is 

 taken to be regular hexagonal. On breaking the mass, a perfect cleav- 

 age parallel to the base of the prism was often observed, besides another 

 cleavage less perfect. The observation of Laurent that zinc cryslal- 

 hzes in rhombic prisms is supposed to be an error. The statement of 

 l^ickles that it also crystallizes in monometrlc or tessera! forms, is not 

 improbable since zinc has many relations to the tesseral metals. The 

 fact shows that zinc is dimorphous. 



2- On the Equivalent of Magnesium ; by IVLVL R. F. Marchand 

 and Th. Scheerer, (Journ. f. prakt. Chem,, vol. 1, heft 8; Phil. Mag, 

 -reb,, 1851, p. 170.)— The uncertainty which still exists as to the true 

 chemical equivalent of magnesium, notwithstanding the numerous ex- 

 periments on the subject, induced the authors to undertake fresh re- 

 searches to settle the question. 



The process which these chemists adopted to determine this point, 

 consists in ascertaining the quantity of carbonic acid contained in a 

 given quantity of native carbonate of magnesia. The mineral which 

 principally served for these experiments is the magnesite of Franken- 

 stem, of which very pure specimens were obtained. The numerous 

 experiments which the authors performed show that the choice of the 

 JJJ*neral is in nowise indifferent. When magnesite contains considera- 

 ble quantities of silica, carbonate of iron, alumina, and especially wa- 

 ter, which if is almost impossible to expel by drying without simultane- 

 ously disengaging small quantities of carbonic acid, it is unfit for the 

 purpose of analysis. # 



, The magnesite of Frankenstein contains only 05 per cent, of for- 

 ^»gn matter, of which an account is taken in the calculations. A cer- 

 ^am quantity of this mineral, well powdered, was introduced into a glass 



