hitelligence and Miscellaneoua Articles. 8 1 



solve it and become yellow, and from them acids precipitate it un- 

 changed, and without the evolution of sulphuretted hydrogen ; after 

 some time, however, the solutions contain some alkaline sulphuret. 



The mean of repeated analyses gave as the composition of this 

 acid,— 



Sulphopianic acid may be considered as opianic acid, in which 2 

 equivalents of oxygen are replaced by 2 equivalents of sulphur = 

 HO + C^° H'* C S'^ ; its formation is therefore very simple. 



These results were obtained by the direct decomposition of the 

 acid, and not of a salt containing it; for M. Wohler found it impos- 

 sible to determine its atomic weight in the latter mode, for he could 

 not obtain salts of silver and lead of constant composition. 



When nitrate of silver is added to a solution of sulphopianate of 

 ammonia, a brownish-yellow precipitate is formed, which is soon 

 converted into blackish-brown sulphuret of silver. When it is 

 quickly filtered it may be dried in vacuo ; its colour nevertheless 

 deepens ; it is then fusible on paper without losing weight. When 

 burnt, it disengages, as the acid does a yellow vapour, and leaves 

 sulphuret of silver. 



Acetate of lead yields a bulky precipitate of an orange yellow co- 

 lour; in twenty-four hours it becomes blackish-brown. Ebullition 

 converts it immediately into sulphuret of lead. — Ann. de Ch. et de 



P%., October 1844. 



PREPARATION OF FERRATE OF POTASH. 



M. Fremy has described several j^rocesses for obtaining the above- 

 mentioned compound ; that which he prefers is the following : — sur- 

 round a Hessian crucible with burning fuel, and put into it 80 grains 

 of pure iron filings, and when these are red-hot, throw upon them 

 160 grains of nitre which has been i)reviously fused and afterwards 

 powdered : the action is instantaneous and very strong ; as a portion 

 of the matter is thrown out of the crucible the experiment should be 

 cautiously performed : the crucible is afterwards to be covered and 

 allowed to cool ; there remains a reddish-violet coloured mass, which 

 is easily detached from the crucible, containing a large quantity of 

 ferrate of potash. I'he product always contains some peroxide of 

 potassium, which is decomposed when it is mixed with water. 



It will be observed that in this experiment the nitre is decomposed 

 by the iron under such circumstances, that the potash does not act 

 upon the silica of the crucible, and the ferrate is not formed unless 

 the action is instantaneous. If the iron be too long heated it be- 

 comes oxidized at the surface, and then the heat requisite for the 

 production of the salt is not excited on the addition of the nitre. 



It is indeed true, that when using the above-mentioned proportions 

 of iron and nitre, but a very small portion of the iron is acted upon : 



Phil. Mag. S. 3. Vol. 26. No. 170. Jan. 1845. G 



