Davy — On some New Organic Nitropnissides. 319 



■and the wasliing was continued till barium chloride failed to indicate 

 the presence of sulphuric acid in the water used in washing the salt. 

 It was then drained and dried, first by being placed betweea blotting- 

 paper, and afterwards by exposing it to the air for some time, till it 

 appeared to be quite dry. When so prepared it had a light-reddish 

 colour and a somewhat glistening appearance ; and, on being placed 

 under the microscope, it was found to consist of prismatic crystals, 

 the prevailing forms of which were six-sided prisms, many of which 

 had wedge-shaped terminations. The salt is only very slightly soluble 

 in cold water, it requiring about 2500 times its weight of that liquid 

 at the ordinary temperature for its solution, and this very small quan- 

 tity of the salt scarcely affects its colour. It is much more soluble, 

 however, in boiling water, of which it requires about 83 times its 

 weight to dissolve it ; and, when saturated at this temperature, it has 

 a faint brownish colour ; and its aqueous solutions are neutral to test- 

 papers. Though it is so sparingly soluble in water, it dissolves 

 readily in rectified spirit. From the amount of silver nitroprusside 

 which a given weight of the thoroughly dried salt yielded, it was evi- 

 dent that two molecules of quinine were combined with one of nitro- 

 prussic acid, and that it was a perfectly analogous salt with the 

 quinine neutral sulphate, and that its composition was represented 

 by the following formula :—(C2oH24N'20o)2. Ho (NO) PeCyg. As to 

 the quantity of water this salt requires for its crystallization, I 

 shall not venture to state ; for the loss which a given weight of the 

 air-dried salt underwent by heating in the water bath was so very 

 trifling, I conclude that it must have lost the greater portion of its 

 water of crystallization in its preliminary drying, and it will require 

 further research to determine this point. 



Before leaving this salt I may add that, when to a cold saturated 

 aqueous solution of quinine neutral sulphate, sodium nitroprusside 

 is gradually added, drop by drop, it produces a reddish- white precipi- 

 tate, which at first re-dissolves, but, on continuing the addition of the 

 nitroprusside, it ceases to disappear, and leaves the mixture turbid ; 

 on its standing, however, for a short time, the precipitate assumes a 

 somewhat crystalline appearance, and after a further interval it sub- 

 sides, forming a somewhat granular deposit, which, on being examined 

 tinder the microscope, is found to consist of short prismatic crystals, 

 radiating from a point in a stellate form ; but the salt, whether preci- 

 pitated from a hot or cold solution, appears to be the same compound. 



The quinine acid nitroprusside was obtained by the following pro- 

 cess : — Some quinine neutral sulphate having been dissolved in 

 water, by the addition of the least possible amount of diluted sulphuric 

 acid ; to this soliition was added gradually sodium nitroprusside. 

 This produced at first a reddish-white precipitate, which, on examina- 

 tion under the microscope, was found to consist of minute, oil-like 

 globules ; these, after a short time, aggregated together and subsided, 

 adhering to the sides and bottom of the glass containing the mixture, 

 in the form of a very sticky and resinous-like deposit ; but this, after 



