268 The Carbuhiidratcx of the Jlaiujold Leaf 



jute bag^ ; the alcoliol is then expressed by means of a Buchner liydraulic 

 press. It is jjenerally (juite colourless and is added to the extract in B. 

 The leaf material remaining is obtained, after the pressing, in a prac- 

 tically dry condition as a hard cake; it is shredded apart and the loose 

 material obtained dried on paper trays in a steam oven for 18 hours; 

 the mass obtained is then weighed on a rough balance (to the nearest 

 centigram), quickly ground in a small mill, and left in an air-tight 

 bottle until it can be analysed. In this material the moisture lost by 

 drying at 110° in vacuo, the starch and 'pentosans are subsequently 

 determined. 



The alcoholic extract, which with washings, amoimts usually to nearly 

 3 litres, if it cannot be immediately analysed (as is usual in a scries of 

 extractions) is transferred to a large bottle, about 10-20 cc. of toluene 

 is added and the bottle closed with a paraffin-waxed cork. We have 

 found, in preliminary experiments, that alcoholic extracts made in this 

 way can be stored for 3 to G months without the slightest changp, 

 even inversion of the cane sugar, occurring. Care should be taken 

 that the solutions are practically neutral or only very faintly alka- 

 line to litmus paper; this is usually the case when ammonia has 

 been added in the proportion stated above, but if any acidity can be 

 detected in the solution it should be corrected by adding the proper 

 quantity of ammonia so as to make the solution jv^t alkaline to litmus. 



The alcoholic extract serves to estimate the total soluble matter 

 and the sugars of the leaf (saccharose, maltose, dextrose, laevulose and 

 pentoses). For this purpose it is evaporated in vacuo (20-30 mm.) 

 in the special apparatus devised for this work (Davis [1913]) which 

 needs practically no attention and enables the 3 litres of extract to be 

 reduced to a small volume (100-150 cc.) in a few hours at a temperature 

 not exceeding 3.5-40°. At so low a temperature all possibility of 

 change in the sugars is obviated. When the extract has been reduced 

 to 150 cc. it is transferred to a 500 cc. measuring (lask^. When much 



' This should always lie boiled with water several times before use to extract any 

 soluble substances (dextrin, etc.). 



- In the case of stalks and midribs the alcoholic extract (usually about 1500 cc.) is 

 evaporated in vacuo to about 2.')-30 cc. : it is then transferred, with washings, to a 100 cc. 

 flask and made exactly to volume. Three portions, each of 10 cc, are used for the 

 estimation of dry mnltcr and the remaining 70 cc. after ]>reeipitation with basic lead 

 acetate (usually 70-100 cc. arc ref|uired) are filtered off on a Buclmer fimncl, and washed 

 until the volume of the filtrate is nearly 500 cc. The excess of lead is removed by adding 

 exactly the necessary quantity of solid sodium carbonate and the solution diluted to 500 cc. 

 25 cc. portions of the clear filtered solution are used to measure the direct reducing and 



