Scientific Intelligence.— Chemistry. 151 



Poppy, - 47 to 50, Fir, - - - 24. 



Almond, - - 46. " Linseed, - - 22. 



Navevv, - - 39. Black mustard, - 18. 



White mustard, -* 36. Heliotrope, - - 15. . 



Tobacco seed, 32 to 36. Beech masts, 12 to 16. 



Kernels of plums, - 33. Grape stones, 10 to 11. 



Idem, 



14. Coloring Matter of Lichen Rocclla, (Antolo 101.) — M. 

 Robiquet having undertaken a diligent examination of the Lichen 

 Rocella, from which a beautiful blue color, used in dying, is ob- 

 tained, has discovered and separated from the other matter, the col- 

 oring principle of this vegetable. The new and singular product 

 which he has obtained, has a very sweet flavor, is easily soluble in 

 water, colorless, crystallizes in beautiful flat quadrangular prisms; by 

 means of a moderate heat, it may be volatilized without decomposing, 

 and does not acquire the coloring property till It has undergone suc- 

 cessively the action of ammonia, and of common air. — Idem. 



15. Researches respecting PJatina^ by M, Dobereiner. (Jalu'b. 

 du Chemie, No. 12.) — (a.) When chloride of platina is dissolved in 

 about 300 parts of water, and the solution rendered sour with muri- 

 atic acid, if zinc, in a metallic state, be plunged into it, a powder is 

 gradually precipitated, which chemists have always, but doubtless er- 

 roneously, (according to M. Dobereiner) considered as pure platina ; 

 for in a state of dryness, this body becomes warm, and assumes a 

 brighter color, if it be exposed to the air and moistened with alco- 

 liol ; lastly it becomes incandescent, particularly after having been 

 treated with nitric acid, when (in contact with the air) it is exposed 

 to a current. of hydrogen gas. 



(5.) When chloride of platina has been treated several times 

 successively with absolute alcohol, at a mild heat, there is obtain- 

 ed at last a brown mass, w^hich easily burns at a higher tempera- 

 ture, but, which dissolved, in a great quantity of alcohol, affords a 

 liquid very fit for being laid upon a glass, so as to form platina mir- 

 rors. For this purpose, dip the glass in the alcoholic solution, so 

 that this last may be uniformlly difflised j then bring it to a red heat 

 in the flame of a spirit lamp. The coat of platina thus produced, 

 affords the brilliancy of a mirror, and adheres so well, that it is 

 impossible to detach it. But if a mirror of this sort be dipped m wa- 

 ter mixed with muriatic acid, and at the same time a plate of zinc 



