August 12,1871.] THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
123 
Copters for ^tukivts. 
CHEMICAL NOTES TO THE PHARMACOPOEIA. 
BY WILLIAM A. TILDEX, D.SC. LOND. 
DEMONSTRATOR OF PRACTICAL CHEMISTRY TO THE 
PHARMACEUTICAL SOCIETY. 
Liquor Plumrt Subacetatis. 
Acetate of lead is boiled with water and oxide of 
lead, the latter in proportion rather larger than is 
expressed by the formula 
Pb (C 2 H 3 0 2 ) 2 3 H 2 0 -fPbO. 
The solution probably contains more than one com¬ 
pound ; but practically it may be looked upon as a 
solution of oxide of lead. Its strongly alkaline re¬ 
action upon test-papers, absorption of carbonic acid 
from the air to form an insoluble carbonate, precipi¬ 
tation of an insoluble sulphate on addition of sul¬ 
phuric acid, point to the relationship subsisting 
between lead oxide and the alkaline earths, baryta, 
strontia, and lime. Liquor plumbi gives insoluble 
precipitates with mucilage of gum-arabic, with 
astringent and colouring matters, and with a large 
number of organic and other acids. Consequently 
it can rarely be mixed with a vegetable infusion or 
tincture without causing turbidity. With tincture 
or wine of opium, for example, the precipitate which 
it causes consists partly of meconate of lead, partly 
of compounds of oxide of lead with the mucilaginous 
and resinoid matters of the opium. In consequence 
of this property, a solution of oxide of lead in acetate 
of lead is frequently employed in the preparation of 
ciystallizable vegetable principles, to remove from 
their solutions the coloured foreign matters with 
which they are naturally combined. 
In making the liq. plumbi subac. dilutus it is 
imperative to use distilled water only, and in no 
case is it proper to clear the solution by the addition 
of acetic acid. 
Liquor Potass.e. 
Four parts of carbonate of potash are dissolved in 
ten parts of boiling distilled water, and then three 
parts of slaked lime are gradually stirred in, the 
ebullition being continued for a few minutes. After 
standing a short time the clear liquor may be de¬ 
canted. It should not be filtered. 
2 KHO + Ca C0 3 = Ca(HO) 2 + K 2 C0 3 . 
[§ It does not effervesce when added to diluted 
hydrochloric acid. Mixed with an equal volume of 
distilled water, it gives no precipitate with solution 
of lime or oxalate of ammonia.] Good liquor potass* 
ought to answer to the first of these tests, but the 
two latter are unnecessarily severe. [§ When it is 
treated with an excess of diluted nitric acid, and 
evaporated to dryness, the residue forms with water 
a nearly clear solution, which may be slightly pre¬ 
cipitated by chloride of barium and nitrate of silver, 
but is unaffected, or but very slightly affected by 
ammonia.] These characters show the absence of 
all but traces of silica, sulphates and chlorides, and 
alumina. 
Liquor potass* contains 5'84 per cent, of KHO. 
Liquor Sodjev —Made in the same manner as liquor 
potass*. It contains 4*1 per cent, of NaHO. The 
chemical equivalent of o'84 of KHO is 4‘10 of 
NaHO. These quantities will saturate the same 
amount of an acid. 
MILK-ANALYSIS BY THE AMMONIA-PRCCESS. 
BY J. ALFRED WANKLYN. 
The ammonia process, which Chapman, Smith, and 
myself applied to water-analysis in the year 1867, is 
available for a great variety of purposes. There is a 
very simple application to the analysis of milk, which 
I propose to describe on the present occasion. 
In our little book on water-analysis, we gave the pro¬ 
portion of ‘ albuminoid ammonia ’ yielded by caseinc as 
7'6 per cent. As we remarked, we could not guarantee 
the absolute purity of the caseine employed for that 
determination. Recent experiments, however, do not 
greatly modify the result. Apparently, the number was 
given a little too high, 6'5 being more in accordance 
with my later experiments. Inasmuch as normal milk 
contains 4'0 per cent, of caseine, 100 parts of normal milk 
should give 0'26 part of albuminoid ammonia,’ and such 
is the result of recent determination. 
In order to examine milk by the ‘ammonia process/ 
the following method of procedure may be adopted. The 
milk is first diluted to a convenient degree; 5 cubic 
centim. (or, preferably, 5 grammes) of milk are placed 
in a 500 cubic centimetre measure, which is filled up 
with water to the 500 c. c. mark; the milk and water 
being then well mixed up together, there results a diluted 
milk. This diluted milk is of such a strength that 
1 cubic centim. contains 10 milligrammes of milk. For 
the analysis, 50 milligrammes of milk— i. e. 5 cubic 
centim. of the dilute milk—is a convenient quantity. 
A tubulated retort, capable of holding about a litre, 
is charged with 400 cubic centim. of ordinary water of 
fair quality, such as, for instance, the ordinary river 
water supplied by the London water companies. Next, 
then, is poured into the retort 50 cubic centimetres of 
alkaline solution of permanganate of potash, made by 
dissolving 200 grammes of solid caustic potash and S' 
grammes of crystallized permanganate of potash in one 
litre of water. The retort is then connected with a Liebig’s 
condenser, by means of a small piece of wide india- 
rubber tube, and heated by means of a good-sized Bunsen 
lamp, the naked flame of which may be applied directly 
to the retort. Distillation then proceeds. The distilled 
water, as it comes over, should be tested for ammonia by 
the Nessler-test, in the manner about to be described, 
and by the time 200 cubic centim. have distilled over, 
will be found to be quite free from ammonia. This 
point having been arrived at, the 50 milligrammes of 
milk (5 cubic centim. of dilute milk) are introduced into- 
the retort, which will then contain 250 cubic centim. of 
water, 10 grammes of potash, and 0'4 gramme of per¬ 
manganate of potash. The distillation is then proceeded 
with as long as ammonia comes over, the ammonia being; 
estimated by the Nesslor test. 
The measurement of ammonia by the Nessler test is 
managed as follows:— 
A solution of iodide of potassium, saturated with binio- 
dide of mercury, is first prepared thus:—35 grammes of 
iodide of potassium, 19 T grammes of bichloride of mer¬ 
cury—are dissolved in less than a litre of water, heat 
being employed to assist the solution of the salts. It 
will be found, that a slight excess of biniodide of mercury 
will remain undissolved—filter or decant so as to separata 
this small quantity of undissolved red iodide of mercury. 
(Should, through failure to have used the proper propor¬ 
tion of the salts, there be no excess of undissolved iodida 
of mercury, a little bichloride must be added, until the red 
precipitate begins to be permanent.) Add, then, either 
120 grammes .of solid caustic soda, or 160 grammes of 
solid caustic potash. Dilute the liquid with water to tha 
volume of a litre, and this is the Nessler reagent. Before 
using the Nessler reagent , add about 5 cubic centims.. of 
strong aqueous solution of corrosive sublimate, which 
will occasion a slight precipitate ; decant oft this preci¬ 
pitate, and the clear liquid is fit for use. This last addi¬ 
tion of corrosive sublimate has for its object the rendering 
of the Nessler reagent sensitive. 
