October 15, 1370.] THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
301 
NEW METHOD OF DETERMINING GRAPE SUGAR. 
BY CARL KNAPP. 
Professor Liebig lias mentioned the fact that 
the addition of prussic acid to a mixture of yeast- 
water with a solution of cane sugar does not prevent 
the conversion of cane sugar into grape sugar by the 
organic substance in the yeast-water. After satu¬ 
rating such a mixture with oxide of mercury, adding 
caustic soda, and heating the liquid to boiling, a 
precipitate of metallic mercury is formed, but no 
such precipitate is formed under the same conditions 
in a solution of cane sugar mixed with an alkaline 
solution of cyanide of mercury. 
Further experiments showed that an alkaline so¬ 
lution of cyanide of mercury is completely reduced 
to metallic mercury by grape sugar, and at the sug¬ 
gestion of Professor Liebig the author of the paper 
undertook to apply this reaction for the determina¬ 
tion of grape sugar. He now gives, as the result of 
liis inquiry, the following method:— 
A solution is made by dissolving 10 grams pure 
dry cyanide of mercury, adding 100 c. c. caustic 
soda solution of 1145 sp. gr. and diluting to 1000 c. c. 
For determining the value of tipis solution, commer¬ 
cial grape sugar was first dried at 100° O., then 
boiled with absolute alcohol till a saturated solution 
was obtained ; the crystals which separated on cool¬ 
ing this solution were taken for use. 
A series of experiments showed that 400 milli¬ 
grams of cyanide of mercury is decomposed by 100 
milligrams of anhydrous grape sugar, on boiling 
them together in an alkaline solution. 
The sugar determination by this method is con¬ 
ducted just as in the Fehling test: 40 c. c. of the 
cyanide solution is heated to boiling in a porcelain 
dish, and the sugar solution, containing about 0 - 5 
per cent., added until the whole of the mercury is 
reduced. The quantity of sugar solution required 
for effecting this reduction ■will contain 100 milli¬ 
grams grape sugar. 
On adding the sugar solution to the boiling allva¬ 
line liquid, a turbidity is at once produced, but this 
disappears again towards the end of the operation, 
and the liquid becomes slightly yellowish. 
In order to judge of the progress of the operation, 
a drop of the liquid is from time to time placed on 
fine Swedish filter-paper laid over a beaker contain¬ 
ing a little strong sulpiride of ammonium. So long 
as any cyanide of mercury remains undecomposed in 
the liquid, a brown spot is thus produced upon the 
paper, and the end of the reaction is indicated when 
such a spot is no longer produced in this way. This 
point may be ascertained much more sharply by 
holding a drop of sulphide of ammonium on a glass 
rod immediately over the paper moistened with a 
drop of the liquid being operated on. 
At first the entire spot becomes brown, but when 
the reaction is nearly terminated, only a pale brown 
ring appears round the edge of the spot; afterwards 
that is to be recognized only when the paper is held 
up to the light, and at last the spot remains quite 
unaltered. With some practice, £ per cent, solution 
of grape sugar can be titrated up to T c. c. 
If at the end of the reaction the spot be allowed to 
dry on the paper, a pale brown ring of sulphide of 
mercury always makes its appearance, inasmuch as 
the solution always contains a trace of grape sugar and 
a trace of cyanide of mercury, either of which is to 
be removed only by an excess of the other substance. 
Third Series, No. 16. 
This circumstance, however, does not interfere with 
the delicacy of the test, provided the coloration of 
the fresh spot be taken as the indication when the 
reaction is completed. 
From a large number of experiments in which 
tills method was adopted and compared with Fe hlin g’a 
test, the author has convinced himself that it is not 
inferior to the latter in accuracy, and though the 
results it furnishes are not better than those obtained 
by Fehling’s method, there is an advantage in the 
new method requiring less tune for making a deter¬ 
mination, and a further advantage in the fact that 
the reduction of cyanide of mercury is not affected 
by foreign substances, such as alkaloids, which in 
some cases interfere with the colour of the suboxide 
of copper precipitate. But perhaps the chief advan¬ 
tage of the new method lies in the easy preparation 
of the standard solution and its capability of being 
kept without alteration .—Annalen der Chemie und 
Pharmacie. 
HYDROBROMATES OF QUININE AND CINCHONINE. 
BY M. LATOUR. 
The successful use of bromide of potassium in af¬ 
fections of the nervous system, and the association of 
this salt with sulphate of quinine, as well as other 
alkaloids, induced the author to prepare hydrobro- 
mate of quinine, in the belief that it might be useful 
as a medicine. 
The hydrobromates of quinine and cinchonine 
were prepared by double decomposition of bromide 
of potassium and the sulphates of the alkaloids, as 
follows:— 
Neutral Hydrobromate of Quinine. 
Basic sulphate of quinine . . 10 grams. 
Alcohol of 85°.50 „ 
Bromide of potassium.... 8 „ 
Distilled water ...... 20 „ 
Dilute sulphuric acid (1 percent.) 10 „ 
The sulphate of quinine and the alcohol are heated 
together in a small flask; the solution of bromide, 
mixed with dilute sulphuric acid, is then added, 
and the whole heated to boiling. After a few minutes 
the sulphate of potash is separated by filtration, and 
washed with hot alcohol. The filtration and washings 
are then evaporated to half the volume, and left to 
ciystallize. After twenty-four hours an abundant 
crop of crystals was formed, and, when pressed be¬ 
tween filter-paper, the salt was white, opaque, of a 
pearly appearance. The salt thus obtained is suffi¬ 
ciently pure for use, though it contains traces of sul¬ 
phuric acid. 
The proportion of bromide of potassium used must 
be rather more than equivalent to the sulphate of 
quinine, otherwise a mixture of basic and neutral 
hydrobromate is produced. It is also necessary to 
add sulphuric acid, in order to make the quinine 
sufficiently soluble, as well as to decompose a por¬ 
tion of the bromide of potassium, so as to produce 
liydrobromic acid, necessary for forming a neutral 
salt with the quinine. 
Basic Hydrobromate of Quinine .—This salt was 
prepared in the same way, but only 5 grams of bro¬ 
mide of potassium were used, together with 10 grams 
of dilute sulphuric acid. A better plan is to dissolve 
1 gram of the neutral salt in 10 grams of a mixture 
of alcohol and water in equal parts. This solution, 
heated to 70° C., is mixed with very dilute ammonia 
