INDIFFERENT LIQUIDS                    235
I last formula. To the clear solution add an equal bulk of
Pe E strong glycerin.
Ipl    336. Glycerin-Gelatin (Brandt's method of preparation t
' M,  -Melted gelatin 1 part, glycerin 1- parts.
The gelatin to be soaked in water and melted in the usual
way. After incorporating the glycerin, the mixture is to be
47I1 filtered. This is a point of vital importance, as the gelatin of
I : commerce is always mixed with particles of dust and minute
1   threads. Swedish filtering-paper does not allow the fluid to
lm 1 pass through sufficiently, and flannel produces more threads
he I than before. The following simple apparatus is found effec-
Al i tive. A wide-necked bottle is broken in two, and the upper
part taken. The neck is stopped with a cork having two holes
is.  bored in it. In the first hole a glass tube about 20 cc. long
4  is inserted so as to project a little into the inside of the bottle
a4  and on the outside it is bent sharply to one side and drawn
Aiis,  out into a point of about 1- to 2 mm. diameter. In the
second hole a funnel-shaped filter is inserted so that the coni-
k.   cal part is inside the bottle and the tube projects a few centi-
tfor  metres beyond the cork and the neck of the bottle.       The
ster,  apparatus is then placed so that the wide opening of the
tI bottle and of the funnel is uppermost, and some spun glass
hid  is pressed into the lower conical part of the filter. In using
h I the apparatus, the funnel is filled with glycerin-gelatin, and
it is  the bottle with hot water, which runs off slowly through the
the  tube in the first hole and is constantly replenished.
,Iof   Some drops of carbolic acid should be added to the fluid
product of the filtering. For mounting, use warm, by melt-
or  ing a small portion on the slide, the object having been
the  previously soaked for some time in a small bottle of the
medium warmed with a suitable apparatus.
337. Glycerin-Gelatin (Kaiser's formula ').-One part by
1 ' Zeitschr. f. Mik.,' ii (1880), p. 69. 'Journ. Roy. Mic. Soc.'iii (1880),
p.502.
2 ' Bot. Cent.,' i (1880), p. 25. 'Journ. Roy. Mic. Soc.,' iii (1880), p. 504.