250 THE EVOLUTION OF LIFE 
a fluid which was faintly alkaline, and the results 
with them have not been so successful, at all events 
for the production of Bacteria, as when | diminished 
the amount of the silicate, and thus rendered the 
solution faintly acid. The first solution I recom- 
mend, therefore, is this :— 
A. Sodium silicate, two, or three, drops.! 
Ammonium phosphate, four, or six, grains. 
Dilute phosphoric acid, four, or six, drops. 
Distilled water, one fluid ounce. 
Another is the solution containing a rather larger 
amount of sodium silicate, its composition being as 
follows :— 
AA. Sodium silicate, four, or six, drops.? 
Ammonium phosphate, four, or six, grains. 
Dilute phosphoric acid, four, or six, drops. 
Distilled water, one fluid ounce. 
The next solution is one containing sodium silicate 
and pernitrate of iron, two varieties of which have 
been used, the first of them having a faintly acid and 
the second a slightly alkaline reaction. Their com- 
position is as follows :— 
B. Sodium silicate, three drops.? 
Liquor ferri pernitratis,® eight drops. 
Distilled water, one fluid ounce. 
BB. Sodium silicate, six drops.? 
Liquor ferri pernitratis, eight drops. 
Distilled water, one fluid ounce. 

' In using the very convenient mixture with equal parts of distilled 
water and sodium silicate, these numbers must, of course, for that 
ingredient, be doubled. See p. 243 also concerning the dropper. 
2 Double the number for the dilute solution. 
3 Of the British Pharmacopceia. 

