70 J. H. Priestley and Dorothy Armstead 
The estimations of the sugar content were made volumetrically 
with standardised Fehling’s solution, using potassium ferrocyanide 
in acetic acid as an indicator of the end point of the reaction (Clowes 
and Coleman ( 5 ), loc. cit. p. 354). 
A known volume of the liquid was then inverted with hydro¬ 
chloric acid for about 15 minutes in a water bath,, cooled, neutralised 
with caustic soda, made up to a known volume and again titrated, 
to see if any further reduction took place after inversion. 
An estimate of the total amount of solute present was made by 
evaporating a measured amount of the liquid to dryness in a weighed 
evaporating basin. This residue gave the weight of the inorganic and 
organic solutes present; it was then heated more strongly till the 
weight was constant, giving the weight of inorganic substances 
present. 
The following results were obtained: 
(1) Estimation of sugars by the reduction of Fehling’s solution: 
Before inversion After inversion Hexose Cane sugar 
0-136 per cent. 0-147 per cent. 0-136 per cent, o-oi per cent. 
Total residue on evaporating to dryness: 0-272 per cent. 
Organic residue 0-206 per cent. 
Inorganic „ 0-066 ,, 
From these results it will be seen that there is evidently some 
other organic substance present in addition to sugars. 
A portion of the sterile juice was therefore evaporated to dryness 
and the organic residue tested for organic nitrogen by heating with 
metallic sodium. The hot tube was then plunged into cold distilled 
water, which was then filtered and tested for cyanide with ferrous 
sulphate, ferric chloride and hydrochloric acid. No prussian blue 
precipitate was obtained and therefore no organic nitrogen was 
present. 
Twenty days after the above quantitative tests the liquid still 
being pumped up was analysed again: 
(2) Estimation of sugars by reduction of Fehling’s solution: 
Before inversion After inversion Hexose Cane sugar 
0-034 P er cent- 0-036 per cent. 0-034 per cent. 0-0019 per cent. 
Total residue on evaporating to dryness: 0-14 per cent. 
Organic residue 0-08 per cent. 
Inorganic ,, 0-06 ,, 
