Nitrogen by A zotobacter and the Growth of the Organism . 875 
used. The first was that which had hitherto been used for the isolation 
and growth of the organism by Professor Bottomley in the Botanical 
Laboratory at King’s College, and consisted of: 
Mannite 
Di-potassium phosphate 
Magnesium sulphate 
Calcium carbonate 
Distilled water 
10 grm. 
2 grm. 
c-2 grm. 
2 grm. 
1,000 c.c, 
50 c.c. of this solution were put into each of seven 300 c.c. Jena glass 
Erlenmeyer flasks, which had previously’ been sterilized. The contents of 
the flasks were then boiled, 50 grm. of quartz sand, which had been 
previously washed, dried, screened, and recently ignited, were added, and 
each flask was plugged and allowed to cool, when the liquids were inocu- 
lated as described above. These flasks were numbered from 1 to 7. 
The second solution employed was a modification of the first, suggested 
by Professor Bottomley, in which 0-2 per cent, of basic slag replaced the 
o-2 per cent, of calcium carbonate. The acidity of the phosphate was 
neutralized by the lime in the slag, which, in addition, contained small 
amounts of the oxides of iron, manganese, magnesium, silicon, and alu- 
minium, as shown in the analysis of the slag given later. The solution 
was thus made up as follows : 
Mannite .... 10 grm. 
Di-potassium phosphate . 2 grm. 
Magnesium sulphate . . 0-2 grm. 
Basic slag .... 2 grm. 
Distilled water . . . 1,000 c.c. 
50 c.c. of this solution were then put into each of seven flasks, which were 
provided with sand slopes and otherwise treated in a manner exactly 
similar to that adopted with the first seven. These were numbered from 
8 to 14 inclusive. 
The third solution tried was that used by Ashby, but only 10 grm. of 
mannite were used per litre, instead of 12 to 20 grm. as advised by Ashby, 
the alteration being made in order to render the solution comparable 
as regards the concentration of the carbohydrate with the preceding ones. 
The solution consisted of 
Mannite .... 
10 grm. 
Mono-potassium phosphate . 
o-2 grm. 
Magnesium sulphate 
o-2 grm. 
Sodium chloride . 
o-2 grm. 
Calcium sulphate . 
o-i grm. 
Calcium carbonate 
5 *° £ rm - 
Distilled water 
1,000 c.c. 
