May 20, 1871.] 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
027 
char in analyses of sugars is not allowable, and that 
the general opinion on the non-absorption of sugar is 
erroneous. 
[That char will absorb a proportion of sugar is con¬ 
clusively proved by the above experiments ; therefore, 
in every exact analysis, its use should be avoided, if pos¬ 
sible. But, in the analysis of low raw sugar, subacetate 
■of lead will not sufficiently decolour the sugar solution 
for the disk to be plainly visible through the solution 
placed in the tube of the polariscope. The use of char 
is then necessary, but the char will in a short time be¬ 
come saturated with sugar from the solution flowing 
through it, and, in fact, only that portion which runs 
through first will be much affected ; so that the only 
precaution necessary is to run off a quantity of the solu¬ 
tion through the char, sufficient to saturate it with sugar 
before filling the tube of the polariscope. That the 
^quantity necessary for saturation may be easily ascer¬ 
tained is shown in the following experiment:— 
A solution of pure loaf sugar, of the ordinary density 
for examination by Soleil’s polariscope, was filtered 
.through 130 cubic centimetres of new char of grist. 
Degree of 
Polarization. 
Before filtration.100* 
1st 25 c.c. of filtered solution . 88-9 
2nd 2.5 c.c. ,, „ . 97‘9 
3rd 25 c.c. ,, ,, . 99‘7 
4th 25 c.c. ,, „ . 100- 
It will thus bo seen that it was needful to run off three 
times the quantity of sugar solution contained by the 
tube of the polariscope before the filtered solution gave 
results unaffected by the absorptive power of char.— 
IEd. S. C.]— American Chemist, from the ‘ Sugar Cane.' 
THE PREPARATION OF FERRIDCYANIDE OF 
POTASSIUM. 
BY WILLIAM T. WENZELL. 
Ferridcyanide of potassium is usually prepared by 
'the 'process of Gmelin, the discoverer of this salt, by 
passing chlorine slowly into a dilute solution of yellow 
prussiato of potash, until the liquid ceases to yield a 
precipitate on the addition of a persalt of iron. The 
•chemical reaction which takes place in this process de¬ 
pends upon chlorine abstracting one equivalent of potas¬ 
sium from two molecules of ferrocyanide of potassium, 
which coalesce to form one molecule of the ferridcyanide 
■of potassium, chloride of potassium being formed at the 
same time, as follows : —2 (K.>Cy, Fe Cy) -f- Cl = K, Cy, 
Fe 2 0y 3 + KCl. . 
This process is no doubt one of the best, and when the 
.action of the chlorine can be interrupted in time to pre¬ 
vent the decomposition of a portion of the product into 
ehloride of cyanogen and various secondary compounds, 
which are known to act injuriously by their presence in 
preventing, to some extent, the subsequent crystalliza¬ 
tion of the salt. This loss and inconvenience is avoided, 
according to Professor Reichardt, of Jena,* by substitut¬ 
ing bromine for chlorine, which will prevent the occur¬ 
rence of the decomposition to which the ferridcyanide is 
liable by the prolonged action of chlorine. Aside from 
:this advantage, the author recommends his process on 
the ground of greater facility with which the salt is pre¬ 
pared. The reaction is in every way identical with that 
of chlorine, the product being ferridcyanide of potas¬ 
sium and bromide of potassium:—2(K 2 Cy,FeCy)-fBr 
= K 3 Cy,Fe 2 Cy 3 -{-KBr. In regard to the economy of a 
process, which calls for the use of bromine,—an article 
■---— 
* Dingler’s Poiytechn. Journal, Dec. 18G9. 
although of late years greatly reduced in value,—few 
manufacturers could be induced to adopt such an expen¬ 
sive substitute. 
The process which I have used for years, and for 
which I claim results as advantageous as the bromine 
process, with the additional desideratum of cheapness, is 
based on the action of chlorine, which is formed and 
made to act upon the yellow prussiate in statu nascenti 
during the process. Four equivalents of hydrochloric 
acid and one of bichromate of potash arc made to act 
upon a boiling solution of ferrocyanide of potassium, 
with the formation of two equivalents of ferridcyanide 
of potassium, three of chloride of potassium, one of 
sesquioxide of chromium, one of water and one of chlo¬ 
rine, as exemplified by the following equation:— 
4 (K 2 Cy, Fe Cy) + K O 2 Cr 0 3 +4 H Cl = 2 (K, Cy, Fe„ Cy 3 ) 
+3 K C1+ Cr, O,, 3 H O -f H 0 + Cl. 
Reduced from equivalent to working quantities, the 
following formula will give satisfactory results:—• 
Bichromate of potash, 1 part, by weight. 
Ferrocyanide of potassium, cryst., 5-72 parts, by weight. 
Muriatic acid, spec. grav. 1TG, 3 parts, by weight. 
Water, 60 parts, by weight. 
Dissolve the two salts in hot water, add the acid, heat 
to boiling, continuing the ebullition, replacing the water 
evaporated during the process until a portion of the fil¬ 
tered liquid is not precipitated on the addition of sesqui- 
chloride of iron. When reaction is completed filter the 
liquid, and wash the hydrated sesquioxide of chromium, 
unite the liquids, and concentrate to crystallization. If 
the evaporated liquid possess an acid reaction, the addi¬ 
tion of caustic potash, in sufficient quantity to cause a 
weak alkaline reaction, will greatly facilitate the subse¬ 
quent crystallization. Generally, there is no difficulty 
experienced by following these processes if the rela¬ 
tive proportions are used in the prescribed equivalent 
amounts. An excess of muriatic acid should be studi¬ 
ously avoided, inasmuch as an excess will contaminate 
the solution of red prussiate of potash with sesquichlorido 
of chromium, which will communicate an emerald-green 
colour, and give a green precipitate of hydrated sesqui¬ 
oxide of chromium on the addition of ammonia.— The 
Pharmacist. 
CALIFORNIA CASTOR OIL. 
The Marysville Appeal has the following account of a 
recent visit to the castor-oil manufactory of Dr. M‘Daniel, 
situated in Marysville:—“ Being a novice in the prepa¬ 
ration and pi’essing of the castor-bean, and the process 
employed to produce the pure oil, we were surprised at 
the simplicity of the machinery and everything con¬ 
nected with the modus operandi. The beans are first sub¬ 
jected to a dry heat of an hour or so in a furnace. This 
softens them and brings them to that peculiar state re¬ 
quired in expeditious pressing. They are then taken 
out and placed in a screw-press, run by horse-power, and 
capable of pressing between 80 and 100 gallons of oil 
per day. From the press the oil is conveyed into a 
vessel, and from thence into a large iron tank or boiler. 
In this is placed 60 gallons of oil and the same amount 
of water, the latter serving to cleanse the oil of all im¬ 
purities. The oil is then boiled about an hour, and kept 
standing until the next morning, when the water is 
drawn off and the oil transferred to the clarifiers, which 
arc composed of zinc, and capable of holding from 60 to 
100 gallons each. After standing about eight hours in 
the sun, it is taken out and put into cans, and is ready 
for the market. Beans of a superior quality are worth 
about $90 per ton, and 100 pounds are supposed to pro¬ 
duce 5 gallons of oil.”— Druggists' Circular and Chemical 
Gazette. 
