28 History of physical Science from [July, 



Dr. Wollaston is of opinion that the crystals obtained by 

 M. Beudant in the preceding experiments are not mere mixtures, 

 but chemical compounds. This he concludes from the trans- 

 parency of the crystals, a quality which they could not possess 

 if they were mere mixtures ; because their constituents differ so 

 much in their refractive power. He found also that crystals 

 could be obtained composed of about four parts of sulphate of 

 zinc and one part of sulphate of copper, which possessed, as far 

 as could be judged, the exact crystalline form of sulphate of iron. 



Sulphate of iron, according to Dr. Wollaston, crystallizes in 

 rhombic prisms with angles of 80-1° and 82°, or more. 



Sulphate of nickel crystallizes in octohedrons, or in four-sided 

 prisms terminated by four-sided pyramids. Sulphate of nickel- 

 and-potash crystallizes in rhombic prisms. — (Anna's of Philo- 

 sophy, xi. 283.) 



I think it right to mention here that the experiments of 

 M. Beudant are not quite so original as he supposes them to be. 

 In the eighth volume of the second series of Gehlen's Journal, 

 published in 1809, there is a very long paper by Professor Bern- 

 hardt entitled " Gedanken uber Kri/sta/logenie and Anardnung 

 der Mineralien, nebst einagen beilagm iibcr olie Krystallisation 

 verschiedener Substanzen." In this paper (page 386) will be found 

 a number of experiments by Professor Bernhardi on the crystal- 

 lization of various mixtures of green, blue, and white vitriol, and 

 the analyses of the resulting salts by Bucholz. Approximations 

 were obtained to the results of Beudant, and we find several 

 curious experiments peculiar to Bernhardi entitled to attention. 



2. Property which Tartar has of dissolving mam/ Oxides. — It 

 has been long known to chemists that the cream of tartar is an 

 excellent solvent of metallic oxides. On that account Gay- 

 Lussac recommends it to our attention as a very useful sub- 

 stance in chemical analyses. 



When we consider the great solvent property of cream of 

 tartar, and that it is even capable of dissolving various oxides, 

 which are insoluble in tartaric acid, as the protoxide of antimony, 

 it is not easy to form an accurate idea of the way in which it 

 acts. Gay- Lussac seems inclined to the opinion that inmost of 

 these combinations it acts the part of a simple acid. According 

 to this view, tartar emetic would be a compound of the acid 

 cream of tartar and of protoxide of antimony. This obscure 

 subject is deserving of further investigation.— (Ann. de Chim. 

 etde Phys. hi. 281.) 



3. Salts of Platinum. — Hitherto very little real progress has 

 been made in the knowledge of the salts of platinum. It has 

 been scarcely possible to obtain the oxides of this metal in a 

 state of purity and capable of uniting with acids ; and when the 

 muriate of platinum is mixed with solutions of other neutral 

 salts, nothing is obtained but triple salts, which vary so much 

 in their appearance and properties that it is difficult to form 

 correct ideas of their composition. Vauquelin has published 



