378 Foreign Literature and Science, 



Silver 58.98 



Antimony 23.4G 

 Sulphur 17.56 



100. 



The mineral examined, was the Red Silver of Andreas- 

 berg. Ann. de Chem. Jan. 1822. 



2. Solubility of Magnesia. — Very different degrees of 

 solubility have been assigned by different chemists, both to 

 pure magnesia and to the carbonate, in hot and in cold 

 water. 



According to Dr. Henry, water dissolves — 



2 oV of magnesia. 

 According to Kirwan, ^gVo 

 According to Dalton, Teio o 

 Dr. Thomson slates it to be entirely insoluble. 

 The same uncertainty prevails with respect to the carbonate. 

 Dr. Murray states that water takes up 2 oVo? ^^d Mr. 

 Brande, that this salt is perfectly insoluble. 



Dr. Fife of Edinburgh has recently examined this sub- 

 ject, and finds that water at 60° dissolves ^^'g „ of its weight 

 of magnesia, and that at the boiling temperature it takes up 

 only 3 6^0 0' Magnesia then, like lime, has the property of 

 being much less soluble in hot than in cold water. 

 It is the same with the carbonate. 

 Water at 60° dissolves ^^jVs 



at 212 9^0 on 



To prove the greater solubility in cold than hot water, it 

 5S only necessary to heat, gradually, a transparent cold solu- 

 tion in a glass with a long narrow neck to prevent too great 

 evaporation. At the instant of ebullition a flocculent mat- 

 ter is precipitated. Ed. Phil. Journal. 



3. Heat. — The power of different substances to conduct 

 heat, by transmitting it from particle to particle internally, has 

 been nev;ly examined by M. Despretz. He finds the con- 

 ducting power of copper to be greater than that of iron, in 

 the proportion of 12 to 5. Zinc and tin do not differ much 

 from iron. The conducting power of lead is less than half 

 that of iron, and five times less than that of copper. Mar- 



