422 Intelligence and Miscellaneous Articles. 



[ 

 cyanide of potassium form the soluble blue, also decomposable by 

 ammonia. The author did not examine the action of ferrocyanide 

 of potassium on any other salts, but thinks it probable that it would 

 be similar upon all the series of salts of iron with organic bases. 



The prussian blue precipitated from a persalt of iron, with the 

 sulphate, nitrate or chloride, is not dissolved by tartaric acid alone, 

 nor is it at all modified by it ; but on adding ammonia to the mixture, 

 it is converted from blue to white, and presents phases of colour ac- 

 cording to the quantity of ammonia added. Thus it becomes violet, 

 purple, amethystine, rose-red, pale red, and then white. This white 

 precipitate becomes blue again by the addition of a fresh quantity of 

 tartaric acid, and passes again to white by ammonia; when exposed to 

 the air and under water, it remains white, and becomes blue by drying. 



The interesting point in this reaction is, that it differs entirely 

 according as a solution of tartrate of ammonia, ready prepared, is 

 poured on the prussian blue, or tartaric acid first and ammonia after- 

 wards. In the first case, the prussian blue dissolves, and the solu- 

 tion is of a magnificent violet colour ; in the second, the precipitated 

 prussian blue is not dissolved, and from blue it soon becomes white. 



The vegetable salt modifies the prussian blue also, but it does not 

 entirely change the colour unless employed in excess. 



Tartrate of ammonia, as first mentioned by M. Monthiers, pos- 

 sesses the property of dissolving prussian blue. M. Calloud states 

 that he had also observed this fact, and had noted it for future ex- 

 amination. — Journ. de Pharm. et de Ch., Septembre 1846. 



PREPARATION OF VALERIANATE OF ZINC. 



M. Lefort remarks that it is perfectly demonstrated, by the nu- 

 merous experiments which have been undertaken to discover an 

 oeconomical mode of preparing valerianate of zinc, that valerianic acid 

 results from the oxidizement of the oil of valerian. 



M. Gerhardt has also found that oil of valerian exposed to the air 

 yields valerianic acid, and it is upon this observation that the new 

 process indicated by M. Brun-Buisson is founded, who remarked 

 that, by exposing the distilled water of valerian for a month to the 

 air, he obtained about 230 grains of valerianate of zinc with about 2 

 pounds of valerian root ; and M. Lefort states that he has repeatedly 

 obtained nearly the same proportion. 



M. Lefort having however examined whether it was not possible 

 to achieve a much more rapid oxidizement than that effected by the 

 air, gives the following as the best process attained : — 



Take of Valerian root . , 2 pounds [av.] 



Water 10 pounds [av.] 



Sulphuric acid 1540 grains 



Bichromate of potash . . 930 grains 

 Powder the root coarsely and macerate it for about twenty- four 

 hours with the sulphuric acid and bichromate in a distillatory ap- 

 paratus and then distil ; the first quarter of water distilled, as it still 

 contains a considerable quantity of oil of valerian, is to be returned 

 to the retort ; the distillation is then to be continued as long as the 

 product acts upon litmus paper. 



