482 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. [December 21 , 1872. 
precaution must be taken (to avoid overlooking 
chloride of sodium, which is slightly volatile) to ig¬ 
nite the residue for as short a time as possible and 
weigh the ash, then ignite very strongly until the 
ash is completely whitened, and reweigh. 
Four samples of genuine milk treated thus gave 
per cent.:— 
Total solids dried 
at 212° F. 
Ash. 
12*12 . . . . 
. . . 0*61 
12*16 . . . . 
. . . 0*63 
12*51 . . . . 
. . . 0*66 
12*47 . . . . 
. . . 0*76 
Genuine milk of average richness, and neither 
skimmed nor watered, contains approximately 12 
per cent of solids, and gives about 10 per cent, of 
cream. Milk which has been skimmed, but not 
otherwise maltreated, contains about 10 per cent, of 
solids. From the departure from these standards 
we can judge of the extent to which skimming and 
watering have been practised, the removal of 1 per 
cent, of cream lowering the solids of milk by 0'2 
per cent. 
Analyses extending throughout a whole year were 
made of the mixed milk of fifteen cows, and they 
show that the milk scarcely ever varies. In but 
four instances did the water fall below 86*6, and in 
four only did it rise above 88 per cent. 
I 11 making a complete analysis of milk, the water 
is found by deducting the weight of solids. 
The fat, by treating the total solids with ether, 
and evaporating down the ethereal solution. 
The milk-sugar is dissolved by water out of the 
milk residue which has been deprived of its fat 
and moistened with alcohol. The aqueous solution of 
milk sugar is evaporated in the water bath and dried 
until constant in weight. The weight of the salts dis¬ 
solved out of the milk residue by water is ascer¬ 
tained by igniting the dry residue containing the 
milk-sugar and is deducted; the difference giving 
of course the milk-sugar. 
The casein, coagulated in the usual way and sepa¬ 
rated by filtration, being on a filter cannot be accu¬ 
rately weighed, and may be found as difference. 
Notwithstanding the statements to be met with in 
works treating of the Adulteration of Food, as to 
sheep’s brains, etc., etc., being occasionally added to 
milk, water is really the only adulterant that is 
ever met with. There can be no doubt that in large 
towns the practice of watering exists to a large 
extent. In London, especially, according to the 
‘ Milk Journal,’ the samples of pure unskimmed 
milk form only a small minority. 
Mr. Wanklyn has lately suggested that his method 
of limited oxidation by means of a strongly alkaline 
solution of permanganate of potash may be very 
well applied to the examination of milk, casein 
yielding 6*5 per cent, and albumen 10 per cent of 
ammonia. I am not aware that he has published 
any experiments bearing upon this, but those who 
have had experience in the estimation of albuminoid 
matters in potable waters, according to his plan, will 
readily understand that it may be adapted with great 
advantage to the examination of milk. 
In a letter received from Mr. J. F. Brown, of 
Lover, in reference to the testing of milk, he suggests 
that a determination of the amount of sugar present 
might form the basis of a convenient and trustworthy 
test. He says, “I remember applying it some years 
ago, by first separating the casein by heating with 
1 per cent, of acetic acid, then diluting the "whey to 
a definite measure and dropping it from a burette 
into a measured quantity of the solution of cupric 
potassio-tartrate, kept boiling hi a llask until the 
colour was discharged. This copper solution was 
made from the directions in Attfield s Chemistry,, 
so that 100 grains was equivalent to 5 grains of 
lactose.”— Ed. Pharm. Journ.] 
PERCOLATION.* 
BY JULIUS SCHWEITZER. 
The subject which I am going to deal with 
in this paper is a pharmaceutical process for 
preparing fiuid extracts, tinctures or any other 
liquid preparation; it is the process called percola¬ 
tion. It is not a new process, although only recently 
introduced into the last edition of the Pharmaco¬ 
poeia. Some thirty years ago, Mr. Deane contributed 
a long paper about this subject, an account of which 
is in the first volume of the Pharmaceutical Jour¬ 
nal ; and so recently as at this year’s meeting of the 
Pharmaceutical Conference here in Brighton, Mr. 
Stoddart gave us the results which he had obtained 
in preparing tinctures by this process and by simple 
maceration. 
The different writers on percolation, after referring 
to the various difficulties which this process presents, 
usually finish by recommending a proceeding of 
then* own, slightly different from those of their prede¬ 
cessors. I consider it, therefore, not out of place to 
bring the subject forward once more. I do not pre¬ 
tend to tell anything original or new, but will simply 
give an account of my proceeding. In working 
for many years in a large laboratory, I have had 
opportunities to try nearly every drug used in phar¬ 
macy, both on the large and small scale, and I never 
found any great difficulties to success. I usually 
carried my experiments 011 with cold water. The 
different opinions of the various writers on this sub¬ 
ject I consider have principally arisen by their 
working with small quantities, if you work on the 
small scale, and if you are careful in the selection 
of your drugs, and see that they are properly pow¬ 
dered, and if you watch the subsequent process with 
the desire to produce a good article, you are almost 
sure to succeed whatever plan you may follow; but 
if you adopt the same proceeding on a large scale, 
the results are not near so certain and satisfactory; 
on the contrary, you find success very doubtful, and 
failure in many instances unavoidable ; and no pro¬ 
cess can be considered sound and recommendable 
that is not applicable for large quantities. I con¬ 
sider also, that a certain amount of confusion and 
difficulty may be caused to a beginner by not keeping 
the two processes of displacement and percolation 
more distinct and separate from each other. That 
there is a difference in these two processes I consider 
sufficiently proved by their different names. 
Displacement .—Displacement means the displacing 
or the removing of the soluble matter from your 
drugs and nothing else, and consequently you re¬ 
move, eliminate or displace this in the highest state 
of concentration, and by means of the least possible 
amount of fluid; it is a process more applicable for 
small quantities where the ingredients are reduced 
* Read at a meeting of the Brighton Association of Phar¬ 
macy, December 6tb, 1872. 
