ON PRUSSIAN BLUE 287 



contained some silver in combination. The residuum was 

 reduced silver. (/) The compound formed by the calx of 

 mercury dissolved in the colouring matter, and crystal- 

 lised (Sec. xii. (h)), yielded, by means of distillation, a little of 

 the colouring matter, but hardly any mark of volatile alkali. 

 In the neck of the retort there was likewise some mercury 

 sublimed, with a portion of the original compound. 



(y) Hence I was disposed to believe that the con- 

 stituent parts of the colouring matter were volatile alkali 

 and an oily substance. In this opinion I was the more con- 

 firmed, when I saw that, on dissolving martial vitriol in 

 spirit of hartshorn, recently distilled, and adding to it 

 muriatic acid, I obtained Prussian blue. I however distilled 

 ox's blood till nothing more would pass over into the 

 receiver, and the retort was red hot. I filtered the liquor 

 of the receiver in order to separate from it the empyreu- 

 matic oil, and then dissolved a little martial vitriol in it, and 

 added a superabundant quantity of acid ; and thus likewise 

 obtained Prussian blue. (h) I then resolved to make 

 several experiments, the principal purpose of which should 

 be to unite the volatile alkali with some oily substance. 

 For this purpose I distilled a mixture of concrete volatile 

 alkali and unctuous oil ; a mixture of the same alkali with 

 animal fat ; and, on another occasion, with oil of turpentine ; 

 a mixture of quicklime, sal ammoniac, and axunge ; the 

 same mixture with oil of hartshorn ; likewise a mixture of 

 potashes, sal ammoniac, and empyreumatic oil ; the same 

 mixture with axunge ; but all in vain. The liquors obtained 

 in the receiver, which consisted of phlegm mixed with volatile 

 alkali and oil, never yielded even the slightest mark of 

 Prussian blue. Hence I concluded that, though aerial acid 

 and phlogiston are obtained every time any oil is decomposed, 

 it at the same time contains water intimately combined with 



