44 POWDERED VEGETABLE DRUGS 



erratic fashion and without specifying the methods followed. The 

 absolute or natural ash content of a drug is obtained when the sample 

 is free of all foreign matter, hence a thoroughly washed average sample 

 must be used. The cleaning and washing must, however, be carefully 

 done in order that none of the tissue may be removed and that none 

 of the salts of the drug may be leached out or washed away and that 

 no foreign salts may be added. A rapid rinsing and washing in dis- 

 tilled water (using a wicker wire holder or container) would serve the 

 purpose. The cleaned sample must then be dried to constant weight 

 at a temperature of 100C. Ashing this cleaned and dried sample 

 gives the absolute ash percentage. This method will yield results as 

 uniform as they can be made, taking into consideration the natural 

 variation in different samples of the same drug. The ash percentage 

 thus obtained would merely serve as a comparative guide to the 

 amount of sand, dirt, clay and other inorganic impurities that may be 

 present in the unwashed commercial sample of the same drug, making 

 reasonable allowance for the natural, incidental and unavoidable 

 impurities present. We will suppose that the absolute ash of an aver- 

 age sample of colchicum corm is 2.0 per cent, and that of the commercial 

 sample under examination yields 5.0 per cent, with 3.0 per cent, of 

 acid insoluble ash. It would be safe to conclude from these data that 

 the drug was very carelessly gathered. Or it might be that the excess 

 of ash was due to the addition of some foreign vegetable substance 

 having a higher ash content than colchicum. The micro-analysis sup- 

 plemented perhaps by chemical tests would determine the quality and 

 purity of the drug. The ash test is in nearly all cases subsidiary and 

 supplementary to. the microscopical examination and to the chemical 

 assay. In many instances the ashing can be omitted. 



For practical purposes it is not necessary to determine the absolute 

 ash content. Determining the ash content of the well-cleaned and 

 garbled drug will answer all practical check purposes. The U. S. P. 

 should state the average ash yield for each vegetable drug, giving the 

 approximate maximum limit with the commercially unavoidable 

 inclusions of clay, dirt and sand. 



