On some new Methods of forming the Nitroprussides. 11 



in colour, and becomes lighter and lighter, till, after it has passed 

 Mead End, it becomes a light yellow (for about fifteen or twenty 

 yards, when it will change again to gray, and so on to the end), 

 striped with bands of iron-coloured sands with little patches of 

 gray in it, which are full of shells. The first five feet of the 

 sands are full of shells not in seams, but this depth diminishes 

 till at about three-fourths of its length, the fossiliferous part 

 runs out altogether. Teeth of Lamna, Myliobatis, iEtiobatis, 

 remains of Crocodile, Trionyx, and Chelone are found here, 

 but in so very brittle a state that they are difficult to save. I 

 have, however, one beautiful small Trionyx (rivosus) found 

 here, and my Collector has found bones of Mammals, but too 

 rotten to preserve. The shells found here are clearly fluvio- 

 marine, consisting of Potamides, Potamomya, Natica, Ampullaria, 

 and Bulla j &c. 



This ends the Hordwell or freshwater strata, the next bed being 

 the first of the Barton or marine series. 



II. On some new Methods of forming the Nitroprussides. By 

 Edmund William Davy, A.B., M.B.T.C.D., Lecturer on 

 Chemistry in the Carmichael School of Medicine, fyc, Dublin*, 



SINCE Dr. Playfair's discovery of the nitroprussides in the 

 year 1849, I am not aware that those interesting com- 

 pounds have hitherto been formed by any process essentially dif- 

 ferent from either of those adopted by him, which consisted in 

 acting on the ferrocyanides with nitric acid, or the binoxide of 

 nitrogen, under certain circumstances. 



My attention being lately directed to this subject, I have 

 ascertained that compounds possessing all the properties of the 

 nitroprussides may be formed by the action of other chemical 

 agents on the ferrocyanides, besides nitric acid or the binoxide of 

 nitrogen. The following are the new methods by which I have 

 succeeded in forming those compounds : — 



1st. By the action of hydrochloric acid on certain ferrocyanides 

 in presence of a chlorate. Thus, when a mixture of ferrocyanide 

 of potassium, chlorate of potash, and dilute hydrochloric acid is 

 made, and these substances allowed to react slowly on each other 

 at the ordinary temperature, there will, after some days, be formed, 

 amongst other products, more or less of the nitroprusside of 

 potassium, which may be recognized by the fine purple or violet 

 coloration produced by a few drops of a soluble sulphuret in a 

 little of the solution of the mixture previously neutralized by an 

 alkaline carbonate; this reaction with soluble sulphurets being 

 highly characteristic of the nitroprussides. 



* Communicated by the Author. 



