436 M. Vauquelin’s Memoir on [Jone, 
“The second portion of gas when agitated with water lost 
half of its volume, and this water had acquired very sensibly the 
smell and taste of hydrocyanic acid. It gave a blue colour to 
litmus paper reddened by an acid, and formed prussian blue 
with the acid sulphate ofiron. It was hydrocyanate of ammonia 
which the water had dissolved. The gas not absorbed by water 
burned likewise with a blue flame, and the product of its com- 
bustion rendered lime-water milky. 
“ The sides of the third jar were covered with a yellow matter, 
which had the appearance of an oil, and which was soluble in pot- 
ash. Water absorbed only a fourth part of this gas. It assumed 
a yellow colour, became alkaline, and acquired a very sensible 
taste of hydrocyanic acid. It produced a great deal of prussian 
blue, with acid sulphate of iron. The insoluble gas was of the 
same nature as in the preceding jars. 
“‘ The salt which had sublimed in the neck of the retort dur- 
ing the distillation of prussian blue was dissolved in water. It 
had a strong smell of ammonia ; its solution was very alkaline ; 
it effervesced with acids; and did not form prussian blue with 
acid sulphate of iron. It appears from this experiment that 
hydrocyanate of ammonia is more volatile than carbonate of 
ammonia. 
“ The residue of this distillation was slightly attracted by the 
magnet. It dissolved without effervescence in muriatic acid, 
and its solution was precipitated greenish-brown by ammonia. 
After the action of the muriatic acid there remained a small 
quantity of prussian blue, which had not been decomposed. 
“« The results furnished by the decomposition of prussian blue 
‘by heat show clearly that it contained both oxygen and hydro- 
gen. But do these two bodies constitute an essential part of 
prussian blue, or do they come from the water which it still 
retained ? This we must examine before we can form an accurate 
opinion respecting the nature of prussian blue. 
“ Without affirming that it is possible to dry prussian blue 
completely without partially decomposing it, we may, at least 
with some reason, think, that the little water which it contains 
cannot resist the action of the fire to the end of the decomposi- 
tion of the prussian blue; the time at which the products 
contain the greatest proportion of oxygen and hydrogen. 
“Having mutually decomposed the requisite quantities of 
sulphate of iron and prussiate of potash dissolved in water, I 
obtained a fine blue precipitate, with which I filled a flask into 
which I had put iron filings. ‘The filings being agitated occa- 
sionally, the blue colour, in the course of a month, assumed a 
tint of green: in the course of another month, the colour became 
of a dirty yellowish white. When the colour seemed to undergo 
no further alteration, I decanted a little of it into a glass, where 
the colour soon became greenish ; and on adding water and 
agitating it assumed a fine blue colour. If prussian blue were a 
