ON PRUSSIAN BLUE 237 



remains in the lixivium sanguinis supersaturated with acids ; 

 for the same mixture, removed into another vessel, imparts 

 to the air the colouring quality, and that repeatedly, 

 according to the quantity of air. (d) When I applied upon 

 the pieces of paper a solution of perfectly dephlogisticated 

 calx of iron, instead of a solution of vitriol, no Prussian blue 

 was formed ; but the muriatic acid dissolved the calx 

 entirely. This agrees with what is said in Sec. n. (d). 



SECTION IV. 



Being now aware that acids really attract the alkali more 

 strongly than the colouring matter does, I wished to know 

 what effect would be produced by distillation, (a) I there- 

 fore poured lixivium sanguinis, supersaturated with vitriolic 

 acid, into a glass retort, luted on a receiver closely, and 

 distilled by a gentle fire. When about one-third of the mass 

 had passed over, I changed (&) the receiver, and distilled till 

 half of the remainder went over, (c) The watery liquor, 

 which came over first, had a peculiar smell and taste. The air 

 in the receiver was filled with the same colouring matter as 

 the glass vessels (Sec. m.) had been ; paper tinged with lacmus 

 was turned red by this liquor ; but upon discovering after- 

 wards, by means of the solution of terra ponderosa, some 

 vitriolic acid in it, I perceived that I could not depend upon 

 this phenomenon for any conclusion. I mixed with one 

 part of this water a little phlogisticated calx of iron, or 

 what comes to the same thing, a little precipitate from 

 vitriolated iron ; and a short time afterwards I added some 

 drops of vitriolic acid to it, by which I obtained a fine 

 Prussian blue, (d) Part of this water being exposed for 

 some hours to the open air, entirely lost its colouring quality. 

 (e) The water obtained by the second distillation (&) pro- 



