25i) 



In the current form the apparatus wants about 1 oc. liquid to 

 ferment. B^y taking a smaller size this volume can be reduced to 

 0.5 cc, but the accuracy of the reading diminishes (intltience of 

 the convex mercury meniscus). For constructive and practical reasons 

 it seems impossible to reduce the size more. 



The quantity of fermentable sugar, used in the apparatus of 

 ordinary size is about 40 mgr. (corresponding with 10 cc. C<J.j) 

 and should not be less than 4 mgr. The last limit is determined by 

 the circumstance, that almost an equal volume of the carbonic acid 

 as is produced from this quantity of sugar by the fermentation is 

 soluble in 1 cc. of the sufficiently fermented liquid under average 

 barometric pressure and at the temperature of the room. By applying 

 a manipulation, viz. the addition of a known, small quantity ferment- 

 able sugar, it" is possible to determine smaller quantities of sugar 

 with this apparatus, but the analysis is not very accurate in that 

 ease. With the developing of small quantities of carbonic acid the 

 influence of the factor, which is to be charged for the gas, dissolved 

 in the fermented liquid, is comparatively very large, and just this 

 factor is by the changing composition of that liquid always some- 

 what uncertain. 



The inoculation-material for this apparatus is a small quantity of 

 yeast, which is taken from a tube-culture with the aid of a thick 

 platinum needle. That yeast quantity is so chosen by Kluyver, in 

 connection with a research of Joulbauhr, that the proportion yeast 

 to sugar is about 1 : 2. The inllueiu-e of the autofermentation is can- 

 celled. With this yeast-concentralion the fermentable sugars have 

 usually completely disappeared after about 40 hours (when raftinose 

 is present the time, necessary for the fermentation is much longer). 

 This long fermentation makes it necessary to sterilize carefully the ap- 

 paratus, the fermenting mixture and the mercury, shutting off the liquid. 



For many biological researches a method for quantitative sugar- 

 analysis would be desirable for quantities smaller than 1 cc. and 

 often it will be necessary to estimate smaller poi'tions than 4 mgr. 

 with greater accuracy than is possible with the aid of the mani- 

 pulation in the ap|>aratus refei'red to. Therefore now an apparatus 

 will be described with which this [jurpose can be reached. The 

 quantities of sugar, which can be fermented are between 3.5 mgr. 

 and 0.1 mgr. and a drop of 0.010 cc. will be sufficient to perform 

 the analysis, though it is preferable to take a larger quantity of 

 the liquid. Moreover it will be evident that with this new method 

 the fermentation will be much sooner finished than with the old 

 one, so that no sterile circumstances are necessary. 



