26 Sketch of' the latest Improvements [Jan. 



atom of the acid would weigh only ^"268, which is considerably 

 less than an atom of each of the constituents, which together 

 weigh 10'829. If, on the other hand, we take the proportion of 

 black oxide of iron and prussic acid as a criterion, the atom of acid 

 ought to weigh 22-485, and it might be a compound of one iroa 

 4- one oxygen + six carbon + five azote + six hydrogen ; besides 

 •which many other numbers might be chosen. These anomalies 

 render Mr. Porrett's analysis of the ferrureted chyazate of potash 

 somewhat doubtful. 



Ferrureted chyazate of barytes he found composed of 



Ferrureted chyazic acid 34'31 



Barytes 49-10 



Water iC>-59 



100-00 

 Ferrureted chyazate of iron is composed of 



1 <i*'-?^ ') 



.. n= ( Ferrureted chyazic acid. . 53-380 

 o4*05 3 "' 



Black oxide of iron . . 19* 



Prussic acid 6^ 



Peroxide of iron 34"235 



Water 1 2385 



100-000 



3. Sulphureted Chyazic Acid. — Mr. Porrett discovered this acid 

 in 1808, by boiling three or four parts of Prussian blue in powder 

 with one part of sulphuret of potash, and a sufficient quantity of 

 water. The new acid is gradually formed, and neutralizes the 

 potash in the solution. Various other processes were attended with 

 success. To obtain the acid from this solution in a state of purity, 

 Mr. Porrett employed the following method: — Add sulphuric acid 

 till the liquid acquires a decidedly sour taste : then keep it for some 

 time nearly at the boiling point. When cold, add to it a little 

 black oxide of manganese, which will turn it to a beautiful crimson 

 colour. Filter the liquid, and add to it a solution containing two 

 parts of sulphate of copper and three parts of prosulphate of iron, 

 till the crimson colour disappears. A copious white precipitate falls, 

 composed of protoxide of copper combined with sulphureted chyazic 

 acid. Boil the precipitate in a solution of potash, which separates 

 the acid, and leaves the oxide of copper. Mix the potash solution 

 with sulphuric acid, and distil. The sulphureted chyazic acid comes 

 over into the reservoir. It is still mixed with some sulphuric acid, 

 from which it may be freed by carbonate of barytes. 



The acid thus obtained is colourless, has a strong smell, analogous 

 to that of acetic acid, and its specific gravity is 1*022. At a boiling 

 temperature it dissolves a little sulphur. This acid consists of two- 

 thirds of its weight of sulphur and one-third of the constituents of 

 prussic acid. The salts which it forms have the following pro- 

 perties : — 



1 



