308 EXPERIMENT STATION RECORD. 



Determination of -water. — Five grams of material is dried in an air 

 bath at a temperature of from 100 to 105° 0. to constant weight. 



Determination of ash. — Five grams of the substance is incinerated in 

 a muffle until the ashes are white or light gray. The Belgian law 

 requires that the amount of matter in the ash insoluble in 10 per cent 

 hydrocholoric acid shall be determined and that it shall not exceed 2 

 per cent. 



Determination of crude protein. — Nitrogen is determined in 1 to 2 gm. 

 of substance by the Kjeldahl method, the protein being calculated from 

 the nitrogen by the use of the factor 6.25. 



Determination of pure albuminoids. — This is done by means of Stut- 

 zer's method as follows: To 1 gm. of the substance is added 100 cc. 

 of water and the solution brought to the boiling point, 2 to 3 cc. of a 

 saturated solution of alum is added, and then a quantity of copper 

 hydrate corresponding to about 0.4 gm. of copper oxid. After cooling 

 the residue is collected on a filter, washed at first with water, and after- 

 wards with alcohol. The nitrogen is determined in the filter and con- 

 tents by the Kjeldahl method without previous drying. The factor 

 6.25 is used in calculating the albuminoids from the nitrogen thus found. 

 If the substance contains an alkaloid it is first boiled on a sand bath 

 with 100 cc. of alcohol containing 1 cc. of acetic acid. The solution 

 thus obtained is decanted through the same filter, which is afterwards 

 used for collecting the copper hydrate precipitate. 



Determination of fat. — For this purpose 3 to 5 gm. of the substance 

 is exhausted in one of the common forms of extractors with carbon 

 tetrachlorid or ether. Commercial ether is redistilled with sodium 

 before use for this purpose, and the sample is dried at 100° O. in the air 

 or in a current of inert gas before extraction with the ether. The 

 extract is collected in 100 to 150 cc. flasks, and after the solvent is 

 driven off, dried for 2 hours at 98 to 100° G. in a hot water bath and 

 weighed. For the determination of substances other than fat which 

 are dissolved by the ether, the residue is redissolved in ether, an equal 

 volume of alcohol is added, the solution exactly neutralized, and evap- 

 orated to dryness. The residue is taken up in ether, filtered into a 

 tared flask, the solvent driven off, and the residue dried for 2 hours and 

 weighed as pure fat. 



Determination of crude cellulose. — Three grams of the substance is 

 boiled for £ hour with 200 cc. of 1.25 per cent sulphuric acid, the 

 liquid being maintained meanwhile at a constant level. After set- 

 tling, the solutionis decanted, and the residue is extracted twice" in the 

 same manner with 200 cc. portions of water. The different extracts 

 are collected in one flask. After settling, the supernatant liquid is 

 siphoned off, the residue is combined with that in the digestion flask, 

 and the whole is treated as described above, first with 200 cc. of 1.25 

 per cent potassium hydrate, and then with 2 successive portions of 

 200 cc. each of water. The extracts thus obtained are treated as above 



