Schiiette^Biochemical Study of Lake Mendota Plankton 607 
for twelve hours. After the subsidence of the suspended mat¬ 
ter, the supernatant liquid was filtered through filter paper 
pulp and the operation repeated. The united filtrates were 
treated with lead subacetate solution and the excess of lead re¬ 
moved from the filtrate with hydrogen sulphide. The lead-free 
filtrates were evaporated under diminished pressure to a small 
volume. A faint, though positive, reaction was obtained with 
Molisch’s alpha-naphthol reagent, but no reaction with orcinol 
solution or orcinol and ferric chloride solution. No pentoses 
are present, yet there are indications of the presence of other 
carbohydrates for the solution showed a slight reducing action 
toward Fehling’s solution. 
The extract from catch 5138 gave with phenylhydrazine 
hydrochloride and sodium acetate an amorphous brown precipi¬ 
tate. A microscopic examination of the latter showed that it 
contained brownish-yellow needles. By the cautious addition 
of a little water, enough were removed for a melting point de¬ 
termination. They charred at 215° C. but did not melt. We 
concluded that they were not crystals of an osazone. The 
small quantity of crystals obtained did not permit of an ex¬ 
amination as to their identity. 
The amorphous precipitate was washed with cold water to 
remove the excess of reagents mechanically held. A part was 
then dissolved in hot alcohol and another part in purified 
pyridine. Ethyl ether was stratified over one portion of the 
pyridine solution and benzol over the other. From neither the 
alcoholic nor the pyridine solutions was a crystalline product 
obtained which would indicate that the precipitate was, or con¬ 
tained an osazone. Further attempts at the isolation of an osa¬ 
zone had to be abandoned on account of a lack of material. A 
smaller amount of furfural was obtained from this catch than 
from the other plant catches. This was to be expected, how¬ 
ever, on account of the presence of the Crustacea in the sample. 
Five grams of catch 5138 were treated for one hour on a 
boiling water-bath with 150 cc. of 50 per cent purified neutral 
alcohol in a 200-cc. flask. The flask was then set aside over 
night. The solution was made up to the mark with 95 per 
cent alcohol and filtered. An aliquot was dealcoholized and 
washed into a 100-cc. flask, basic lead acetate solution was 
added and volume made up to the mark with water. It 
was then filtered and the lead removed from the filtrate with 
