JtLY 16, 1870.] 
THE PHARMACEUTICAL JOURNAL. 
57 * 
Hydrocyanic acid may be detected with certainty, 
even when present in minute quantity, by one of tlie 
folowing processes:— 
a. [§ Treated with a minute quantity of a mixed 
solution of sulphate and persulphate of iron, after¬ 
wards with potash, and, finally, acidulated "with 
hydrochloric acid, it forms Prussian blue.] 
_---- 
71. 6HCN + FeS0 4 + 2KHO + 4KHO + d(HO 
Hydrocyanic Ferrous Potash, 
acid. sulphate. 
= K 4 (Fe"C 6 N 6 ) + K 2 S0 4 + 6H 2 0 + a-KHO. 
Ferrocyanide. Sulphate. Water. 
II. 3K 4 Fe"C 6 N 6 + 2Fe"' 2 Cl 6 + aKHO + aHCl 
Ferrocyanide of Ferric 
potassium. chloride. ^ 
z: Fe f, 4 3 (Fe"C ? N 6 ) + 12KC1 + a(KCl+H 2 0). 
Ferric ferrocyanide, 
or Prussian blue. 
b. Mixed with a few drops of solution of sulphur 
in sulphide of ammonium, evaporated to dryness, and 
then moistened with weak solution of ferric chloride, 
a red stain of ferric sulphocyanide is produced. 
I. (NH 4 ) 2 S + HCN + s 
Sulphide of Hydrocyanic 
ammonium. acid. 
= (NHJHS + (NH 4 )CNS. 
Sulphydrate of Sulphocyanide of 
ammonium. ammonium. 
II. Fe^Clg -f 
Ferric chloride. 
= 8NH.C1 
Chloride of 
ammonium. 
6 (NH 4 ) CNS 
Sulphocyanide. 
+ Fe 2 (CNS) 6 .. 
Ferric sulphocyanide. 
Alkaline cyanides give no precipitate with a sniau. 
quantity of nitrate of silver. So long as the propor¬ 
tion of nitrate of silver to cyanide is not more than 
one molecule to two, a double salt is formed, which 
remains in solution. ^_ 
KCN + KCN+ AgN 0 3 = KCN,AgCN + KN0 3 . 
When even the minutest quantity of nitrate is 
superadded, a white precipitate of cyanide of silver 
begins to form. 
KCN, AgCN + AgN0 3 = 2AgCN + KN0 3 . 
Upon this fact is based the official quantitative 
test. 10,000 c.c. of the vol. sol. of nitrate of silver 
contain 170 grams (= 1 molecule) of the silver salt, 
and if this quantity were added to 2 molecules or 54 
grams of HCN, rendered alkaline by the addition of 
soda, the liquid would remain clear, but the next 
drop would produce a precipitate of cyanide of silver. 
Now, if 10,000 c.c. indicate the presence of 54 
grams of H C N in the liquid tested, the employment 
of 100 c.c. in the same manner, will indicate tuo of 
54, or '54 gram of HCN. 
The quantity of dilute acid which, according to 
the B. P., contains this amount is 27 grams, which 
corresponds to two per cent, of real acid; for if 2 / 
contain ‘54 what w T ill 100 contain ? 
27 : 100 :: -54 : x. 
x = 2. 
Hydrocyanic acid is very liable to decomposition, 
but is more stable when mixed with a little mineral 
acid ; much of the commercial preparation therefore 
contains a minute proportion of HC1. The. chief 
products of its spontaneous change are formiate of 
ammonia— 
HCN + 2H 2 0 = NH 4 CH0 2 , 
and a brown substance, the nature of which is not 
understood. 
Hydrocyanic acid is also found among the products 
of the action of water upon bitter almonds. These 
seeds contain a crystalline principle, amygdaline , 
and another substance of ill-defined albuminoid 
character, the composition of which is not known, 
called emulsin or synaptase. When both are dis¬ 
solved in water, the latter, by some unexplained in¬ 
fluence, causes the amygdaline to decompose. 
C 20 H 27 N O n + 2H 2 0 
Amygdaline. 
= C 7 H 6 0 + 2C 6 H 12 0 6 + HCN. 
Essential oil Glucose. Hydrocyanic 
of almonds. acid. 
On distilling the mixture, the essential oil and 
most of the hydrocyanic acid pass over. The aqua 
laurocerasi, B.P., contains HCN, produced by a re¬ 
action probably similar. 
Utlmto. 
Characteristics of the Principal Wines we Drink. 
By A. Dupre. London: Robert Hardwicke, 192, 
Piccadilly. 
In a short pamphlet, reprinted from the ‘Popular Science 
Review,’ Dr. Dupre has given, some interesting particu¬ 
lars relating to the common wines to be met with in the 
wine trade in this country. Towards the end of the 
pamphlet we notice a very complete table of analyses of 
Hock, Claret, Hungarian wine, Greek wine, Sherry, Port, 
and Marsala. The analyses are of recent date, and by 
himself; and, even if there were nothing else m the 
paper, they would render it a valuable contribution 
towards the chemistry of wine. 
BOOKS RECEIVED. 
A System of Botanical Analysis, applied to the 
Diagnosis of British Natural Orders. For the 
Use of Beginners. By W. Handsel Griffiths, Ph.D. 
London: Wyman and Sons, 74, Great Queen Street, Lin¬ 
coln’s Inn Fields. 1870. 
Science for the People: A Memorandum.of Various 
. Means for Propagating Scientific and Practical Know¬ 
ledge among the Working Classes,.etc. etc. By Thomas 
Twining, Vice-President of the Society of Arts. London : 
C. Goodman, 407, Strand. 1870. 
Treatise on Fermentation ; on the Source of Muscu¬ 
lar Force and Nutrition. By Justus von Liebig, 
President of the Bavarian Academy of Sciences. Munich. 
F. Straub. 1870. 
The Food Journal. No. 6, Vol. I. London: J. M. John¬ 
son, 3, Castle Street, Holborn. 
Transactions of the Odontological Society of Great 
Britain. No. 7, Vol. II. London: Wyman and Sons, 
74, Great Queen Street. 
Essay on the Cultivation of Cinchona. By Ch. Be¬ 
langer, Director of the Botanical Garden of Martinique. 
Reprinted from the ‘ Revue Maritime et Coloniale, April, 
1870. Paris: Paul Dupont, 41, Rue Jean-Jacques Rous¬ 
seau. 
Die Pflanzenstoffe in chemischer, physiologi- 
SCHER, PHARMAKOLOGISCHER UND TOXIKOLOGISCHER 
Hinsicht. By Drs. Aug. and Theod. Husemann. 
Second Part. Berlin: Julius Springer. 1870. 
