Mar. 24,1923 
Determination of Starch Content 
1003 
an electric mixer for periods of 5 minutes three or four times. Filter to 
obtain a clear extract. (It may be necessary to return the first portions 
of the filtrate to the filter.) Mix the infusion well. 
PREPARATION OP CHARGE 
Weigh out a definite charge of from 2 to 6 gm. 22 of the finely pul¬ 
verized and well-mixed sample, 33 using the smaller charges in the case 
of materials containing much gel-forming substance. (The weight of 
starch in the charge must not exceed 1.5 gm.) Transfer to a dry filter 
paper held in place. 24 in a glass funnel of the usual type. It is not 
necessary to use a hardened filter; any tight, high-grade paper, 12^ or 
15 cm. in diameter, will be satisfactory. 
EXTRACTION OP CHARGE 
Extract the charge with 5 successive portions of ethyl ether, taking for 
each portion more than enough to cover the charge. Use a cover glass 
to retard evaporation. After completing the extraction, allow the ether 
to evaporate and extract the charge with weak alcohol. The concentra¬ 
tion of the alcohol may be varied somewhat to suit the material under 
examination. For linseed meal 35 per cent alcohol (by volume) must be 
used, while for dried apple pomace 25 per cent alcohol is best. Use 300 
cc. of the alcohol to obtain the required thoroughness of extraction. 
Follow this with several filterfuls of 95 per cent alcohol, and finish the 
leaching operations with a second ether extraction. (It is convenient to 
have the charge stand overnight at this point to allow the ether and 
alcohol to evaporate, as alcohol must be eliminated before starting the 
digestion with malt.) 
Start the preparation of the malt infusion. 
A correction for the dextrose in the malt extract is obtained by con¬ 
ducting a control determination, preferably in duplicate. Starting with a 
piece of the filter paper extracted with alcohol, distilled water is added, 
and the control is carried along side by side with the actual starch deter¬ 
mination, being subjected to the gelatinization temperature, receiving 
the same quantities of malt extract, and being treated similarly in every 
respect. 
GElvATlNIZATION 
To return to the primary determination, transfer the paper and charge 
(free from more than traces of alcohol) to a 300 cc. Erlenmeyer flask, and 
mix well with from 20 to 30 cc. of distilled water, macerating paper and 
material to give a perfectly smooth paste. Add 100 to 125 cc. of boiling 
water. Mix quickly, but thoroughly, and with constant stirring. Then 
heat the contents of the flask until it boils freely. In the case of muci¬ 
laginous materials like linseed meal it is necessary to transfer the flask 
to a boiling water bath to complete the gelatinization. Gelatinize thor¬ 
oughly, without scorching or adhesion of the material to the bottom of 
the flask. The mixture should be smooth and free from lumps. 
** Charges of 4 gm. for linseed meal, or 3 gm. for dried apple pomace, have been found to be satisfactory. 
** The entire sample should be ground to pass freely through a sieve of not less than 40 mesh to the inch. 
It is preferable to have the material sufficiently fine to freely pass a 60 -mesh sieve. 
** An ordinary paper dip serves well to clamp the paper in place. 
