488 
DR. PLAYFAIR ON THE NITROPRUSSIDES, 
Symbols : — a 100, Z(010, el01,r0ll,mll0, x211. xis common to the zones em,ra. 
The angles between the normals to the faces are,— 
o 
ha 90 0 
ea 68 16 
ee' 43 28 
rb 62 26 
rr' 55 8 
ma 52 38'5 
mb 37 2T5 
mm! 74 43 
rm 68 25 
re 34 34 
em 77 1 
xm 49 24 
en 27 37 
V 
b 
Nitroprusside of sodium resembles very much in appearance the ordinary red 
prusside of potassium when the latter salt is crystallized from alkaline solutions*. 
Nitroprusside of sodium is not at all deliquescent, but is very soluble in water, 
dissolving in times its weight of water'f' at 60°. It is still more soluble in hot 
water, but appears to have a point of less solubility at a particular temperature, for 
it may easily be crystallized by keeping its hot solution on the sand-bath, while it 
may not do so on cooling. 
It is decomposed by mixing it with excess of alkali, and suffers the singular trans- 
formations with sulphurets of the alkaline metals which have been already alluded 
to. It undergoes no change in weight when heated to 212°, and therefore does not 
lose water in the water-bath. 
The following analyses were made by heating the salt with sulphuric acid, and 
estimating the iron as peroxide, the sodium as sulphate of soda: — 
Analyses I. and II. were made upon a salt obtained by acting on nitroprusside of 
iron with caustic soda. Analyses III. and IV. from a salt prepared from nitroprusside 
of copper. Analyses V. VI. and VII. from the process last described, by acting on 
yellow prusside of potassium with nitric acid and neutralizing with carbonate of soda ; 
and analyses VIII. and IX. from another preparation in the same vray. 
r I. 1 T800 grs. gave 3*300 grs. peroxide of iron and 5*870 grs. sulphate of soda. 
In. 10*300 grs. gave 2*930 grs. peroxide of iron and 5*000 grs. sulphate of soda. 
* Red prussiate of potash crystallizes more easily and with much greater beauty from alkaline than from 
neutral or acid solutions ; the reason being that the excess of alkali decomposes a small quantity of a green 
precipitate, which crystallizes along with it. 
t 50’12 grs. saturated solution at 60° gave 14'46 salt; in another experiment 42'8S grs. solution gave 
12'45 grs. salt, both being dried in water-bath. 
