237
INGREDIENTS REACTING.
RESULTS.
f 3 eq.Water.27‘
2eq.Cryst. \l H -W- ,1
Ferrocvan. ( Seq.Cyan. <3eq.Cyanog. 78-Potassium 4261 Potasm.l98)3eq. Potas «».120-1 eq. Cyan. Potassium.... 66
l 2 eq. Cyan. Iron .108
6eq Protohy'i. ( 6 eq. Water . 54
3 eq. Poth. 144
.3 eq. Water .27
.3 eq.HydrocyanicAcid 81
.3 eq. Water
51 eq. Biferrocyanide
^ Potassium .
6 eq. Water .
»3 eq. Bisulphte. Pot h .
174
54
384
The salt here called biferrocyanide of potassium, is termed, by Mr-Everitt, yellow salt. I have prepared it with the greatest care, but havealways found it to be white. Gay-Lussac also says it is white {Ann.Chim. et Phys. t. 46, p. 77). By exposure to the air it becomes blue.
(, b .) By the action of hydrochloric acid on cyanide of silver. —Thisprocess, proposed by Mr. Everitt, yields an acid of uniform strength, andmay be followed when the acid is required for immediate use. ThePharmacopcDal directions for its performance are (or rather ought to be)as follows:—Add 48)- grains of cyanide of silver to a fluidounce of dis-tilled water, mixed with 39 j grains of hydrochloric acid. “ Shake all thesein a well-stoppered phial, and, after a short interval, pour off the clearliquor into another vessel. Keep this for use, the access of light beingprevented.” The proportions directed by Mr. Everitt are 40 grains ofcyanide, 7 fluidrachms and 20 minims of water, and 40 minims of dilutehydrochloric acid (sp. gr. 1-129). This gentleman says, that practi-tioners could obtain an ounce of the acid, prepared by this process, forone shilling, while the manufacturer could obtain 50 per cent, profit by it.
The theory of the process is as follows :—By the mutual reaction ofone equivalent or 134 parts of cyanide silver and one equivalent or 37parts of hydrochloric acid, there are obtained one equivalent or 144parts of chloride of silver, and one equivalent or 27 parts of hydro-cyanic acid.
INGREDIENTS REACTING. RESULTS.
1 eq. Hydrocya'. A d . 27
1 eq. Cyanogen1 eq. Silver . .1 eq. Hydrogen1 eq. Chlorine.
1 eq. Cyan de . Silver 134 )1 eq. Hydrochi'.Acid 37 ^
(c.) By the action of hydrochloric acid on bicyanide of mercury. —AtApothecaries’ Hall hydrocyanic acid was formerly prepared from onepart of bicyanide of mercury, one part hydrochloric acid (sp. gr. T15),and six parts of water. The mixture w'as distilled until six parts hadpassed over. The acid thus obtained had a sp. gr. O'995, and itsstandard strength was such, that two fluidrachms of it dissolved 14grains of the red oxide of mercury, thereby indicating a strength of about2 - 9 per cent, of real acid.
The most convenient method of procuring concentrated or anhydroushvdrocyanic acid, is by the action of strong liquid hydrochloric acid onbicyanide of mercury. The vapour should be passed over carbonate oflime, to deprive it of hydrochloric acid; and over chloride of calcium,to remove the water. The receiver should be immersed in a freezingmixture, consisting of ice and chloride of sodium.
The theory of the process is as follows:—Two equivalents or 74 partsof hydrochloric acid react on one equivalent or 254 parts of thebicyanide of mercury, and form one equivalent or 274 parts of the bichlo-