Chemical Science. 209 



previously been done by others, and which is well known to the 

 scientific world, an attempt will be made in the following lines 

 to present to view the result of M. Berzelius' labours. 



The first object was, to ascertain the proportion of the iron 

 to the other base in the ferro-prussiates. The salt with base of 

 potash was first examined ; it was purified by fusion, solution, 

 and crystallization, after which it lost nothing by exposure to 

 air for two days, but at a temperature of 140° Fahr. effloresced 

 and diminished between 12.9 and 12.4 per cent. ; it did not 

 then lose weight by a heat above that of boiling water : two 

 grammes (30.89 gr.) of this salt thus dried, were mixed with 

 sulphuric acid ; it heated a little, but suffered no further change 

 till its temperature was raised by a spirit-lamp, when sul- 

 phurous acid and hydrocyanic acid were liberated. The heat 

 was continued till all excess of sulphuric acid was driven off 

 and the mixture then dissolved in warm water containing a 

 little muriatic acid ; the solution was precipitated by ammonia 

 and the oxide of iron, collected, washed, and dried ; it weighed 

 in different experiments between .4 and .43 of a gramme (6.41 gr.). 

 The solution was then evaporated, and the sulphate of am- 

 monia separated by heat, in which operation it was found 

 advantageous to introduce a small piece of carbonate of am- 

 monia in a spoon into the covered crucible : in this way 1.894 

 gramme (28.25 gr.) of sulphate of potassa were obtained. The 

 mean result of several experiments similar to the above, gave 

 the following proportions for some of the elements of the 

 pure prussiate of potassa : 



Potassa 44.62 containing 7.58 = 2 of oxygen. 



Protoxide of iron 16.64 3.79 :== 1 



Water 12.7 11.3 =3 



Loss 26.04 



from which it results that the potassa contains twice as much, 

 and the water thrice as much oxygen as the iron in the state of 

 protoxide. 



The ferro-prussiate of baryta was prepared from prussian 

 blue and the hydrate of baryta. When heated, and the residue 

 analyzed, it gave 



Baryta 51.273 containing 5.38 =2 of oxygen. 



Protoxide of iron 11.865 2.7 =1 



Water 16.56 14.72=5.5 



Loss 20.302 



Here also the proportion between the oxygen of the baryta 

 and that of the protoxide of iron is as 2 to 1. 



The ferro-prussiate of lime, prepared in the same manner at 

 the former salt, was obtained in crystals, of which 100 parts 

 gave, 



Vol. XI. P 



