ON THE PllOCESS OF PERCOLATION. 
393 
Mr. Tomlinson had tried some experiments with different liquids, but he 
thought water was that which would be principally employed. It could be 
easily obtained in a state of purity, and was cheaper than any other. 
Mr. Hanbury inquired if it was necessary to use a magnifying glass for 
examining the figures. 
Mr. Tomlinson said the figures were always large enough to be thoroughly 
examined with the naked eye. 
Professor Bentley could but express his admiration of the manner in which 
the subject had been brought before them. It was quite a new field of obser¬ 
vation, but now that it had been introduced to their notice he hoped it would 
be further investigated and applied to practical purposes. The examination 
of oils and the determination of impurities in them was attended with many 
practical difficulties, and any process that would aid in these investigations 
would be very acceptable to those w r ho had occasion to work upon the subject. 
Mr. Tomlinson had referred to balsam of copaiba as one of the oils that gave 
a characteristic figure ; he should be glad to know if any experiments had been 
made with wood oil, which had been used as a substitute for, as also to adul¬ 
terate balsam of copaiba. lie had been requested by Mr. Deane to direct Mr. 
Tomlinson’s attention to linseed oil, which at present was very difficult to procure 
of good quality. 
Mr. Tomlinson said he had experimented with w r ood oil and had noted the 
figure afforded with it, but he was not yet satisfied with his results, and in¬ 
tended to make some further experiments. 
Mr. Burden supposed this method of testing would be applicable to cod- 
liver oil, and if it afforded a satisfactory means of detecting adulteration in 
that oil it would be valuable. 
Mr. Tomlinson had applied it to cod-liver oil, but he was not sure that the 
samples he had used were genuine. 
ON THE PROCESS OE PERCOLATION OR DISPLACEMENT AS 
APPLIED TO THE PREPARATION OE TINCTURES, AND ON 
A NEW FORM OF PERCOLATOR. 
BY MR. SANGER. 
There have already been published in the journals within the last two years 
some very excellent papers on this subject which treat of the results obtained by 
different operators ; one in particular I might mention, by Mr. Proctor, but, as 
far as I can understand him, he, like those who preceded him, lets the difficulty 
of reducing the ingredients to a proper size, according to the different drugs, be 
the stumbling-block in the way of the general adoption of the process. Mr. 
Proctor’s process entailed sifting the ingredients through sieves of certain di¬ 
mensions, which is attended with a good deal of trouble, and by the separation 
of the more easily from the less easily pulverized portions of vegetable drugs is 
calculated to give uncertain results. On the other hand, when fine powders are 
used, they are liable to swell on being packed in the percolator and then wetted, 
and they thus become an impervious mass. It has been recommended, however, 
to obviate this inconvenience by treating the powder first with just sufficient 
liquid,—literally speaking, to lay the dust,'—that is, so that the powder may be 
stirred about without the dust of it flying up, and yet not sufficient to make it 
into masses. I foresaw that it must not be with each drug I must battle, but 
that some insoluble ingredient must be found to divide the particles of the 
powder. I made experiments with two—powdered-glass and sand. The former 
I had to resign on the score of economy ; and, as a useful ingredient, nothing- 
equals pure silver-sand. This, however, has been opposed as being impure. 
So certain specimens may be, but, as a rule, it is very fairly pure ; yet, as a pre- 
