[ 84' ] 



present in the sample, 3 grams of the powdered cake should 

 be measured out on a watch glass and left in the water-oven 

 to dry. After a few hours it is weighed again. After another 

 hour it is weighed a third time, and when it is found to remain 

 constant in weight since the last weighing, the difference from 

 the original weight is calculated as being due to loss of 

 moisture in 3 grams. At the two last weighings the usual 

 precautions of cooling the substance inside the desiccator, 

 covering it up with another watch-glass and fastening them 

 together by means of the clip should be taken. 



(2) Ash or mineral matters. Two grammes of the cake 

 should be weighed out in the platinum crucible, already 

 cleaned, ignited and cooled in the desiccator. The cake 

 is ignited on the Bunsen flame. When rendered quite 

 white, i. e. } after about half an hour, it is set aside in the 

 desiccator to cool. When cool, it is weighed, and the 

 difference between this weight and the weight of the 

 crucible alone is due to the ash ingredients in the 2 

 grammes. 



(3) Fibre^ or indigestible and insoluble organic matter. 

 3 grams of the sample should be weighed out into a beaker. 

 Two scratches should be made on the side of the beaker, 

 one at 150 c. c. and the other at 200 c. c. 150 c. c. of distilled 

 water should be added to the cake, and the beaker placed on 

 the wire gauze over the flame. The whole is brought to 

 boiling heat with continual stirring to prevent burning. At 

 this stage 50 c. c. of an H 2 SO 4 solution containing 5% of pure 

 H 2 SO 4 are added to the mixture; and the boiling continued 

 exactly for half an hour after that. The normal volume of 

 200 c. c. is maintained throughout by the addition of hot 

 water at intervals during the half hour. The residue from 

 this acid-digestion is collected over a filter on a piece of 

 linen rag. It is washed several times with hot water while on 

 the rag ; and then when it ceases to turn litmus paper red, it 

 is transferred to a beaker. 150 c. c. of water are added again, 



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