OF MICROSCOPIC OBJECTS. 179 
use those given in that work. For red, however, vermilion, 
as above stated, may be used; but it must be carefully 
examined by reflected light to see whether it be free from 
all colourless crystals or not. It must first be worked in a 
mortar, and then the whole thrown into a quantity of water 
and stirred about; after leaving it not longer than a quarter 
of a minute, the larger portions will settle to the bottom, 
and the liquid being poured off will contain the finer powder. 
This may then be dried slowly, or added to the size whilst 
wet in the manner before advised. 
13. Yellow injection—To prepare this, take— 
Acetate (sugar) of lead ......... 380 grains. 
Bichromate of potash ............ 15 
BC ee ae taiaaiche mann sicimsaiuecinn cs -e 8 ounces. 
-Dissolve the lead salt in the warm size, then add the bichro- 
mate of potash finely powdered. 
Some of the chromic acid remains free, and is wasted in 
this solution, so the following is given :— 
Aectate of lead... .aseeserescen ieee 190 grains. 
Chromate of potash (neutral) .. Se LOORS iw 
BIEZON Wed. ates Snipers aba sceanictebnnsabwiare 4, ounces. 
The first of these has the deepest colour, and is the most 
generally used. 
14, White injection.—This is a carbonate of lead :— 
Pecobates OF lead | .....0.cc.ceceeeee 190 grains. 
Carbonate of potash....... “ARE Soe 855 
i SE as ead ene Bip eae 4 ounces. 
Dissolve the acetate of lead in the warm size, and filter 
through flannel; dissolve the carbonate of potash in the 
smallest quantity of water, and add ito the size: 143 
grains of carbonate of soda may be substituted for the cars 
bonate of potash. 
N 2 
