a New Class of Sails. 213 



19*54 : 20"03, while the proportion, 5 equivs, : 25 equivs., or 

 1 : 5, would require 19*54 : 20*93 of carbon. Throughout 

 all the salts, this less quantity of carbon refuses to enrol itself 

 in the simple proportion of 1 : 5, and necessitates the use of 

 the much more complex one of 5 : 24. The above formula 

 may be expressed as Fe^Cy^^SNO, 5Na+10HO. 



Nilroprusside of Potassium. 



12. This salt may be obtained in several ways. 1. By 

 acting upon prusside of potassium with nitric acid, exactly as 

 described under nitroprusside of sodium, but the neutraliza- 

 tion of the acid is effected by carbonate of potash, instead of 

 carbonate of soda as therein described. The nitrate of potash 

 is crystallized out and the mother-liquor is put in the hot 

 chamber to crystallize. 2. It may be prepared from the 

 nitroprusside of iron, or better from the copper salt, by de- 

 composing it with caustic potash, care being taken to keep 

 the nitroprusside in excess. 



Properties. — This salt, from its great solubility, is somewhat 

 difficult to crystallize. It is apt to deposit in an amorphous 

 form ; but this may be avoided by a little practice, and fine 

 large crystals may be obtained. These crystals belong to the 

 oblique system, and have been measured by Prof. Miller. 



Symbols'. — bO\0, m 110, s012, elOl, rill. 



Angles between normals to the faces : — 



The axis of the zone mb, makes an angle of 57° 56' with 

 that of the zone rb, and an angle of 71° 0' with the axis of the 

 zone sb. 



This salt dissolves in its own weight of water at 60°; 60*06 

 grs. of a saturated solution of this salt evaporated in the water- 

 bath left 30*40 grs. of the salt. It is not precipitated from its 

 solution by alcohol. With caustic potash it unites and forms 

 a salt which is described in a further part of the paper. Nas- 

 cent hydrogen does not decompose it. Hydrogen, chlorine 

 and sulphurous acid were passed through both cold and hot 

 solutions of the salt without effecting any change. It is^lightly 

 deliquescent, and acquires a greenish shade when exposed to 



