Potassium phosphate 1.0 gramme
Magnesium sulphate 0.5 gramme
Calcium chloride 0.01 gramme
Sodium chloride 2.0 grammes

and dissolve in

Distilled water 1000 c.c.

2. Fill into flasks, in quantities of 20 c.c. and add to each a small
quantity of freshly washed magnesium carbonate.

3. Sterilise in the steamer at 100 deg. C. for twenty minutes on each of
three consecutive days.

4. Add to each flask containing 20 c.c. solution, 2 c.c. of a sterile 2
per cent. solution of ammonium sulphate.

5. Incubate at 37 deg. C. for forty-eight hours and eliminate any
contaminated culture flasks. Store the remainder for future use.

~Winogradsky's Solution (for Nitrous Organisms).~--

1. Weigh out and mix

Ammonium sulphate 1 gramme
Potassium sulphate 1 gramme

and dissolve in

Distilled water 1000 c.c.

2. Add 5 to 10 grammes basic magnesium carbonate, previously sterilised
by boiling.

3. Fill into flasks and sterilise, etc., as for previous solution.

~Silicate Jelly (Winogradsky).~--

1. Weigh out and mix

Ammonium sulphate 0.40 gramme
Magnesium sulphate 0.05 gramme
Calcium chloride 0.01 gramme

and dissolve in

Distilled water 50 c.c.

Label--Solution A.

2. Weigh out and mix

Potassium phosphate 0.10 gramme
Sodium carbonate 0.60 gramme

and dissolve in

Distilled water 50 c.c.

Label--Solution B.

3. Weigh out

Silicic acid 3.4 grammes

and dissolve in

Distilled water 100 c.c.

4. Pour the silicic acid solution into a large porcelain basin.

5. Mix equal quantities of the solutions A and B; then add successive
small quantities of the mixed salts to the silicic acid solution,
stirring continuously with a glass rod, until a jelly of sufficiently
firm consistence has been formed.

6. Spread a layer of this jelly over the bottom of each of several large
capsules or "plates."

7. Sterilise in the steamer at 100 deg. C. for thirty minutes on each of
three consecutive days.

_Media for the Study of Water Bacteria._

~Naehrstoff Agar (Hesse and Niedner).~--(_For enumeration of water
organisms._)

1. Weigh out: agar, 12.5 grammes and emulsify in 250 c.c. distilled
water.

2. Wash the agar emulsion into a tared 2-litre flask with a further 250
c.c. distilled water.

3. Dissolve by bubbling li