5. Distribute 100 cc. or larger known quantities in flasks large enough
to hold the other ingredients which are to be added later.
6. Sterilize in the autoclav at 15 lbs. (120° C.) for 15 minutes after
the pressure reaches 15 lbs.
7. Prepare a 10 per cent. solution of basic fuchsin in 95 per cent.
alcohol, allow to stand 20 hours, decant and filter the supernatant
fluid. This is a stock solution.
8. When ready to make plates melt 100 cc. of agar in streaming steam or
on a water bath. Dissolve 1 gram of lactose in 15 cc. of distilled
water, using heat if necessary. Dissolve 0.25 gram anhydrous sodium
sulphite in 10 cc. water. To the sulphite solution add 0.5 cc. of the
fuchsin stock solution. Add the fuchsin-sulphite solution to the lactose
solution and then add the resulting solution to the melted agar. The
lactose used must be chemically pure and the sulphite solution must be
made up fresh.
9. Pour plates and allow to harden thoroughly in the incubator before
use.