1816.] during the Year 1815. 35 
When paper stained with litmus is left in contact with it for some 
days, the colour of the litmus is destroyed. When this acid is 
heated, the greatest part of it is volatilized, though a portion of it 
is decomposed into oxygen and chlorine, Muriatic acid, sulphureted 
hydrogen, and sulphurous acid, decompose chloric acid, and deve- 
lope chlorine, provided they be not added in excess, With muriatic 
acid, water is formed, and the two acids are converted into chlorine. 
With sulphureted hydrogen, sulphur is deposited, water formed, 
and chlorine disengaged. The sulphurous acid is converted into 
sulphuric by taking oxygen from the chloric acid, which in conse- 
quence is converted into chlorine. 
3. Acetic Acid.—It is the custom in Germany to distil vinegar 
in stills, whose heads and conducting pipes are composed of Englisl: 
tin. Professor Pfaff, of Kiel, has shown that vinegar distilled in 
this way holds a little tin in solution. Accordingly, when sul- 
phureted hydrogen is mixed with it, a dark brown precipitate 
appears. This precipitate had been ascribed to lead; but Pfaff 
ascertained that it is always owing to tin, even when soft solder is 
present, which contains a notable proportion of lead. 
4. Prussic Acid.—From a set of experiments published by Dobe- 
Teiner, it would appear that when an alkali is heated with pure 
charcoal, ammonia is always formed ; but when, besides the char- 
coal, iron, or any substance containing iron, is present, prussic 
acid, or rather ferrureted chyazic acid, is formed. 
A sketch of Gay-Lussac’s researches respecting prussic acid has 
been inserted in the last number of the Annals of Philosophy. He 
has shown that it is a compound of equal volumes of cyanogen and 
hydrogen gas. Hence it consists of 
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It may be obtained by pouring muriatic acid upon cyanide of 
mercury. The receiver must be surrounded with ice. Gay-Lussac 
has given it the name of hydro-cyanic acid. It possesses the follow- 
ing properties :— 
It is a colourless liquid, having a very strong smell. Its taste is 
at first cooling, then hot, and it is a violent poison. Its specific 
gravity is 06969. It boils at the temperature of 80°, and congeals 
at the temperature of 5°. When exposed to the air, it begins to 
evaporate, and produces a degree of cold sufficient to congeal it, 
The specific gravity of its vapour is 09360. This acid combines 
with the different bases, and forms the salts at present known by 
the name of prussiates. Henceforth they must be called hydro- 
anates. Potassium, and potash, soda, and barytes, at a red heat, 
ecompose hydro-cyanic acid, and produce cyanides, 
5. T he substance discovered by Berthollet, and called by him 
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