Chemical Science. 395 



a a 



xzzW. ~" =s grains of p 

 a — b 



TF-^ = TT.ll£=r grains of q. 

 a—b 



Say that 200 grain measures of the test are equivalent to 10 

 grains of muriate of soda, then 10 grains of muriate of potash 

 would require 157.9 grain measures (nearly) of the same test. 



Suppose that we have 178.95 grain measures exhausted in one 

 experiment in 10 grains of a mixture of the two salts — 



Then *=w^=io X IZL££zi 5 I^.= 1 oxiL£i 



a — b 200-157.9 42.1 



= 5 grains of muriate of soda. 



And ^-^^"- c -i,w 200-178. 95 _ 1rw 21.05 



a — b 200—157.9 42.1 



= 5 grains of muriate of potash. 



9. On the Solution of Steel and Iron in Acids, and on the residua 

 which remain. By M. Karsten. — M. Karsten observed, as others 

 have done, that the action of acids on steel depends on the hard- 

 ness of the metal ; hard steel being dissolved with great diffi- 

 culty and slowness in diluted acids. White raw iron shows the 

 same habitudes as steel, but in a more striking manner. Diluted 

 muriatic, or sulphuric acid, has scarcely any effect on it ; and 

 the black powder does not appear until weeks have elapsed: 

 strong hot muriatic acid dissolves it, leaving no residuum. Sul- 

 phuric acid, in the same circumstances, leaves some carbon, black 

 and of a metallic appearance. Cold nitric acid separates black 

 flakes, which, by long exposure to the acid, become brownish-red. 



Gray raw iron exhibits very different appearances. Diluted 

 muriatic and sulphuric acids act but slowly, and leave, after 

 months, a carbonaceous residuum in very different conditions ; one 

 part is in thin leaves, or scales, lustrous, metallic in appearance, 

 capable of resisting acids and alkalis, not attracted by the magnet, 

 and very slowly combustible in a red-hot crucible: these are 

 graphite. Another part has a similar appearance ; but is mag- 

 netic, and resembles the residuum from soft steel. A third part 

 is black, not magnetic ; colours alkaline solutions black, and is 

 readily consumed by heat and air. Of these three bodies, the 

 graphite is never missing; the others seldom occur together. 

 Strong muriatic acid does not leave so much graphite, part being 



