Davy — On some New Organic Nitroprus&ides. 317 



power whatever of developing the characteristic reaction of strychnine- 

 tinder the circnmstances stated. But to retui-n to the sodium nitro- 

 prusside ; my experiments on that salt fully confirm the statement of 

 those two chemists already mentioned, as to its incapability of develop- 

 ing the pui-ple reaction when added to a mixture of strychnine and 

 sulphuric acid. 



I shall now describe the reaction of sodium nitroprusside on a 

 soluble salt of strychnine, and point out some of the properties of the 

 resulting nitroprusside of that alkaloid. When a solution of the 

 former salt is added to one of the latter, there will he immediately 

 formed a dull reddish-white precipitate, which, on being examined 

 under the microscope, will be found to be in great part of a crystalline 

 character, consisting of very fine prismatic crystals. On heating the 

 mixture, the precipitate will dissolve ; and on cooling, it will re- 

 appear in a lighter and more completely crystalline form, the crystals 

 being arranged in a peculiar brush or fan-shaped manner, or radiating 

 from a point in all directions. Some of this salt which had been pre- 

 cipitated by a solution of sodium nitroprusside, and was washed and 

 dried in the way already described, was taken and heated in the 

 water-bath till its weight remained constant, and the loss sustained by 

 a given quantity was noted. The thoroughly-dried salt was then 

 dissolved in water, and precipitated by a solution of silver nitrate, and 

 the silver nitroprusside so formed ascertained. Prom these two 

 results — viz., the amount of water lost by drying, and of silver nitro- 

 prusside obtained — agreeing most closely with the amounts which 

 should by calculation be furnished by a salt having the formula 

 (C,iH,2j!^o02)^Ho(^^0)FeCy5 + 3HoO, where two molecules of the 

 base are combined with one of the acid, plus three atoms or 

 molecules of water of crystallization, there can therefore be no 

 doubt that this formula expresses the composition of the salt, 

 at least as regards the relative proportions of the base and acid. 

 As to the water of crystallization, there is not the same certainty, 

 for this salt readily loses such water by exposure to the air at the 

 ordinary temperature, and consequently it is difficult to remove 

 the moisture without its losing at the same time more or less of the 

 water necessary for its crystallization. Its composition shows that it 

 is a neutral salt, and test-papers indicate the neutraKty of its solutions. 

 As to its solubility in water, I found by the means already described 

 that it required about 847 times its weight of cold, and very nearly 

 66 times its weight of boiling, water for its solution. 



It dissolves but slowly and in comparatively small proportion in 

 rectified spirit, either hot or cold, and is only very slightly soluble in 

 chloroform, and still less so in ether, and does not appear to be dis- 

 solvable by benzole. 



I may observe, as regards the ciystallization of this salt, that, 

 though it usually assumes one or other of the forms already described, 

 yet, when it very slowly crystallizes from its aqueous, or more particu- 

 larly alcoholic solutions, it presents itself, at least in part, under the form 



