Dayy — On some New Organic Nitro])russides. 315 



I have ascertained, that nitroprussic acid forms (as might have been 

 expected from its being a bibasic acid) two classes of salts with the 

 alkaloids, viz., neutral and acid salts. In the first there exist twa 

 molecules of the base and one of the acid, and in the second one mole- 

 cule of each. 



I have also observed that some of the alkaloids — as, for example, 

 morphine, strychnine, and bnicine — seem to be capable of forming- 

 only neutral salts, whereas others — as those of quinine, cinchoniue, 

 and nicotine — form both neutral and acid salts, in combining with 

 nitroprussic acid. I have noticed also that where the alkaloids form 

 the two classes of salts, that in some cases the neutral salt is the most 

 readily crystallizable, and the acid one much less so, and vice versa : 

 thus the quinine neutral salt crystallizes with great facility, whereas 

 the acid salt does so with difficulty ; on the other hand, the nicotine 

 acid salt readily assumes the crystalline form, whereas the neutral 

 one appears to be non-crystallizable. 



In ascertaining the composition of those nitroprussides which I 

 have discovered, some of which I shall presently describe, the mode I 

 adopted was to dissolve a given weight of the thoroughly dried salt in 

 water, which, in the case of the more sparingly soluble salts, it was 

 necessary to be hot, or even boiling, for this purpose ; and then, by the 

 addition of a solution of silver nitrate, to precipitate their nitroprussic 

 acid in the form of the insoluble nitroprusside of that metal, and from 

 the amount of that salt so obtained to calculate the quantity of nitro- 

 prussic acid which had been combined with the alkaloid. 



As to the water oE crystallisation given in the case of some of the 

 crystalline salts, its amount was determined in the following manner : 

 The nitroprusside from which the moisture had been as far as possible 

 removed by filtering or blotting-paper, and afterwards by exposing the 

 salt to the air at the ordinary temperature, till it appeared to be quite 

 dry, a given quantity of it was taken and heated in a water-bath till 

 its weight remained constant, when the loss thus sustained was 

 regarded as water of crystallization ; but as it was difficult to ascertain 

 whether the salt in the first instance had been quite freed from 

 mechanical moisture, or had not lost some of its water of crystalliza- 

 tion by the exposure to the air (as it is well known many salts will do 

 when so treated), the amounts of such water, given in the formulfe of 

 some of the salts to be described, represent the quantities that agree 

 most closely with the results obtained by treating the salts in the 

 manner just stated ; but, for the reasons mentioned, those results will 

 require to be confirmed by further research, before they can be taken 

 as representing the true amounts of water necessary for the crystalli- 

 zation of those salts. 



I may here further add, that the mode I adopted to determine the 

 degree of solubility of the different salts in water, at its ordinary tem- 

 perature, and at its boiling point, was to saturate water at those tem- 

 peratures with the salt, and then taking a given bulk of the solution — 

 the weight of which, of water alone, at such temperatures was known 



