METHOD OF ANALYSIS FOR THE MOEE IMPORTANT 

 CONSTITUENTS OF PLANTS. 



I 



PRELIMINARY OPERATIONS. ESTIMATION OF MOISTURE 

 AND ASH. 



4. Drying. In the majority of cases the parts of plants at 

 our disposal for analysis have already been dried, and we can only 

 take account of the small amount of moisture that has been 

 absorbed from the air in consequence of the hygroscopic nature 

 of the vegetable tissue in contact with it. I can only recommend 

 that the estimation of moisture, for which a temperature not 

 exceeding 110 will as a rule suffice, be made with a small 

 quantity of the substance. I should not advise the drying of the 

 material intended for use in the investigations to be discussed in 

 the following chapters, because, even at a temperature of 100 to 

 110, a number of constituents prone to decomposition undergo 

 chemical change. It will be sufficient if the moisture be estimated 

 in about 2 to 5 grams, that is, if that quantity be kept at the tem- 

 perature indicated till it ceases to lose weight. By means of this 

 determination the results of all other estimations can be calculated 

 to the dry substance. 1 



1 An apparatus for drying material for agricultural (chemical) analysis has 

 been described by Hugo Schulz (Landw. Versuchsstat, vol. ix. p. 213) ; one 

 for the rapid estimation of water in organic substances by Gawalovski in the 

 Zeitschrift f. anal. Chemie, xiii. 267 (1874). Tor the determination of 

 moisture in fruits rich in sugar, such as apples, etc., Tschaplowitz (ibid. Jg. 19, 

 p. 243, 1880), recommends the slices to be first extracted with absolute 

 alcohol containing 10 to 20 per cent, of ether, and then dried at 100 to 110, 

 the ether-alcohol solution to be evaporated, the residue heated to 85 to 90 and 

 then added to the dry stibstance. See also Keischauer in the Jahresb. f. 

 Pharm. Jg. 1867, p. 8 (Amer. Journ. Pharm. xxxviii. 74) ; Schoonbroodt, 



