352 Analysis of Scientific Books and Memoirs. 



to their formation is the difficulty and frequently the impossibility of ren- 

 dering the salts perfectly anhydrous before their solution in alcohol is 

 attempted. 



11. An Account of the Tracks and Footmarks of Animals found Im- 

 pressed in Sandstone in the Quarry of Corncockle Muir. By the Rev. Dr 

 Henry Duncan. — A full abstract of this very curious paper has already 

 been given in this Journal, No. xvi. p. 305. See also No. xv. p. 130. 



12. On the Combination of Chlorine with the Prussiate of Potash, and 

 the presence of such a Compound as an Impurity in Prussian Blue. By 

 Mr James F. W. Johnston, A. M. — The new compound described in 

 this paper is considered as a chloro-ferro-cyanide of potassium, and con- 

 sists of 



1 atom chloro-ferro-cyanic acid == 31 ) 



4 potassium = 20 J 



This new acid may be obtained in a separate state by various processes, 

 which Mr Johnston promises to explain in a future paper. When pure, 

 it forms beautiful red four-sided needles, not differing in appearance from 

 those of any of its salts. 



Mr Johnston has formed the various salts resulting from the union of 

 this acid with the base ; and he gives the following account of their gene- 

 ral properties. : — 



1. They are all of a deep red colour, crystallizing in four-sided pyramids 

 and rhomboidal prisms. In minute needles their colour is golden -yellow. 



2. In the moist state the crystals are liable to decompose by light and 

 heat, becoming externally of a greenish colour, and in solutions depositing 

 a green sediment. 



3. They are very soluble in water, but insoluble in alcohol, unless con- 

 siderably diluted. 



4. Their solutions, when hot and concentrated, have a peculiar smell, 

 approaching to that of weak chlorine ; and, with the exception of the salt 

 of lead, they have all a bitterish taste ; that of lead having the sweet taste 

 of its other salts. 



5. These solutions are decomposed by sulphuretted hydrogen beebming 

 green and depositing sulphur. Some of the hydro-sulphurets have a simi- 

 lar effect, but they are not changed by hydrogen gas. 



6. Treated in powder with sulphuric acid, they give off chlorine gas. 

 From the salts of bary tes, strontian, and lead, it is also partially driven off 

 by a gentle heat. 



7. Their solutions are also decomposed by metallic mercury being 

 changed into green, becoming greenish-yellow, and letting fall a blue pre- 

 cipitate ; the solutions no longer giving a red, but a white, with nitrate of 

 silver. They have likewise a strong action upon metallic iron, coating it 

 immediately with Prussian blue. 



8. They all give similar precipitates with the metallic oxides. 



9. When dry they undergo no change by exposure to the air, the salt 

 of cadmium excepted, which deliquesces. 



