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MOUTH-BACTERIA AS EXCITERS OF FERMESTATION. — 109
The formula for the inactive ethyhdene hietate of zine is
Dried at ordinary temperature it contains 27.3 per cent, zinc
oxide. The result obtained fi^om the analysis difters, therefore,
fr(^m that deduced from the formula by less than 1 per cent.,
and settles beyond doubt tlie fact that the suV)stance analyzed
was the lactate of zinc, or tliat the acid generated by the fermen-
tation is lactic acid, or, more exactly, inactive ethylidene lactic
acid, since, as shown above, the acid solution was optically
inactive, and the zinc salt contained three molecules of water of
crystallization. The salt was furthermore soluble in sixtj'-two
parts water at 14° C.
I repeated the analysis with the followino: solution :
Water, 1000 cc.
Saliva, 300 cc.
Bouillon, 200 cc, made by boiling 125 grams of beef ten
minutes in 300 cc. of water.
Sugar, 10.0.
This solution being slightly acid was neutralized with the car-
bonates of lime and sodium, sterilized, and infected from a pure
culture of the bacterium in question. It was treated throughout
exactly as above described, except that the zinc salt was con-
verted into the sulphide instead of the carbonate, and burned
with powdered sul})hur in a stream of hydrogen. The result was :
Substance analyzed = 1.0540
Zinc sulphide ^= 0.415
Zinc = 26.38 per cent.,
instead of 26.74 per cent., as deduced from the formula, a differ-
ence of only one-third of one per cent.
In this case the substance was dried at 100° C. before Aveigh-
ing, and the formula becomes
IZn
c:h:o:^^°=-^^-
One more analysis was made, using
Water, 1000 cc.
Liquid beef extract, 20 cc.
Suffar, 10.0.
MOUTH-BACTERIA AS EXCITERS OF FERMESTATION. — 109
The formula for the inactive ethyhdene hietate of zine is
Dried at ordinary temperature it contains 27.3 per cent, zinc
oxide. The result obtained fi^om the analysis difters, therefore,
fr(^m that deduced from the formula by less than 1 per cent.,
and settles beyond doubt tlie fact that the suV)stance analyzed
was the lactate of zinc, or tliat the acid generated by the fermen-
tation is lactic acid, or, more exactly, inactive ethylidene lactic
acid, since, as shown above, the acid solution was optically
inactive, and the zinc salt contained three molecules of water of
crystallization. The salt was furthermore soluble in sixtj'-two
parts water at 14° C.
I repeated the analysis with the followino: solution :
Water, 1000 cc.
Saliva, 300 cc.
Bouillon, 200 cc, made by boiling 125 grams of beef ten
minutes in 300 cc. of water.
Sugar, 10.0.
This solution being slightly acid was neutralized with the car-
bonates of lime and sodium, sterilized, and infected from a pure
culture of the bacterium in question. It was treated throughout
exactly as above described, except that the zinc salt was con-
verted into the sulphide instead of the carbonate, and burned
with powdered sul})hur in a stream of hydrogen. The result was :
Substance analyzed = 1.0540
Zinc sulphide ^= 0.415
Zinc = 26.38 per cent.,
instead of 26.74 per cent., as deduced from the formula, a differ-
ence of only one-third of one per cent.
In this case the substance was dried at 100° C. before Aveigh-
ing, and the formula becomes
IZn
c:h:o:^^°=-^^-
One more analysis was made, using
Water, 1000 cc.
Liquid beef extract, 20 cc.
Suffar, 10.0.
