650 EXPERIMENT STATION RECORD. 



laboratory, to use a dish with a hhie ring on the iuside at the 200 cc. 

 point. After boiling, the solution is allowed to settle and the clear 

 li(|uid removed, according to Henneberg and Stohniann, with a small 

 siphon or, according to Wattenberg, by means of a funnel covered Avith 

 gauze over which lilter paper is placed, the funnel being inverted in the 

 liquid and the stem connected with a suction pum]) or a sii)hon. The 

 residue is boiled for one-half hour with 200 cc. of water, and the water 

 removed as before, and this boiling with water is repeated. (Where the 

 suction tilter is used, Wattenberg states that it is not necessary to 

 bring the water to boiling the second time, but that it can be siphoned 

 oft' immediately.) 



A mixture of 50 cc. of 5 per cent potassium hydroxid and 150 cc. of 

 ^ater — i. e., a 1.25 per cent solution — is now added to the residue, l)oiled 

 for one-half hour, drawn off as before, and the residue boiled twice 

 with water, as described above. 



The residue is then collected on a tared filter previously dried at 

 105° C, washed with hot water until the alkaline reaction disap- 

 pears, several times with hot alcohol and with ether, dried at 105°, 

 and weighed. 



The crude liber obtained in tliis way contains a little inorganic mat- 

 ter, and usually some nitrogen. Accordingly, it is incinerated and the 

 ash deducted; and in very exact determinations the nitrogen must also 

 be determined, multiplied by 0.25, and the i)rotein deducted. 



Holdetleiss' proposed to carry on the digestion with acid and alkali in 

 pear-shaped bulbs of about 300 cc. capacity, the boiling being effected 

 by conducting steam into the bulbs. At the end of the treatment the 

 bulbs are dried with the residue at 100 to 105° C, weighed, and the 

 crude liber incinerated in a crucible, and the ash weighed and deducted. 

 To simplify the drying of the crude fiber, Stift- made the bulb in two 

 parts, the substance being collected in the lower part, which was 

 removed for drying. 



According to the official method in the Uuite<l States,^ 2 gm. of sub- 

 stance previously extracted with ether is boiled with 200 cc. of 1.25 per 

 cent suli)huric acid for one-half hour in a flask with a reflux condenser, 

 filtered, the residue boiled for one-half hour with 200 cc. of 1.25 per 

 cent sodium hydroxid, with a reflux condenser as before, filtered through 

 a Gooch crucible, washed^ dried at 100° C, weighed, incinerated, and 

 the ash deducted. 



The Holdefleiss method of boiling with steam in bulbs and the Ameri- 

 cau method differ essentially from the original method, and may give 

 somewhat different results. 



'Landw. Jahrb. 1877, Supplement, p. 103; Eieler and Schneidewind, Versnchs- 

 Station Halle; and E. S. R., 5, p. 459. 



"Oesterr. ungar. Ztscbr. Zuckeriud. and Landw., 1895, !>. 35. 



^Association of Official Agricultural Chemists at Chicago, 1893 (U. S. Dept. Agr., 

 Division of Chemistry Bui. 38, p. 190). 



