5. Distribute in test-tubes, 10 cc. to each tube, or in larger
containers, as desired.
6. Sterilize in the autoclav at 15 lbs. (120° C.) for 15 minutes after
the pressure reaches 15 lbs.
g. _Litmus or Azolitmin Solution._
The standard litmus solution shall be a 2 per cent. aqueous solution of
reagent litmus. Powder the litmus, add to the water and boil for five
minutes. The solution usually needs no correction in reaction and may be
at once distributed in flasks or test-tubes and sterilized as is culture
media. It should give a distinctly blue plate when 1 cc. is added to 10
cc. of neutral culture medium in a Petri dish.
The standard azolitmin solution shall be a 1 per cent. solution of
Kahlbaum’s azolitmin. Add the azolitmin powder to the water and boil for
five minutes. The solution may need to be corrected in reaction by the
addition of sodium hydrate solution so that it will be approximately
neutral and will give a distinctly blue plate when 1 cc. is added to 10
cc. of neutral culture medium in a Petri dish. It may be distributed in
flasks or test-tubes and sterilized as is culture media.
h. _Litmus-lactose-agar._
Litmus-lactose-agar shall be prepared in the same manner as nutrient
agar with the addition of 1 per cent. of lactose just before
sterilization. The reaction shall be a faint pink with phenol red, or,
if on titration with phenolphthalein the reaction is not already between
neutral and +1, adjust to neutral. One cc. of sterilized litmus or
azolitmin solution shall be added to each 10 cc. of the medium just
before it is poured into the Petri dish, or the mixture may be made in
the dish itself.
i. _Endo’s Medium._[209][214][215] _To Make One Liter._
1. Add 5 grams of beef extract, 10 grams of peptone and 30 grams of agar
dried for one-half hour at 105° C. before weighing, to 1,000 cc. of
distilled water. Boil on a water bath until all the agar is dissolved
and then make up the loss by evaporation.
2. Cool the mixture to 45° C. in a cold water bath, then warm to 65° C.
in the same bath without stirring.
3. Make up lost weight, titrate, and if the reaction is not already
between neutral and +1 adjust to neutral.