998 
Journal of Agricultural Research voi. xxm, No. z« 
This method was tedious and open to the objection that nothing 
definite was known as to the fate of the interfering carbohydrates, other 
than the mucilage, during the taka-diastase digestion. Furthermore, 
Horton (4) questioned the validity of the conclusion of Davis and Daish, 
that starch was quantitatively converted by taka-diastase into maltose 
and dextrose. 
REVISED METHOD 
The apparent solubility in rather strong alcohol of the conversion 
products obtained through a properly conducted malt-diastase diges¬ 
tion of starch was considered. 9 Experiments were undertaken to test 
the feasibility of using strong alcohol as the medium for separating such 
starch conversion products from mucilage or other interfering p ly- 
saccharids. Neither the dextrine nor any other conversion product 
obtained by digesting starch with an infusion of barley malt (under 
conditions fully described on p. 1003--1004) was thrown out of solution 10 
by alcohol of 60 per cent strength. Starch determinations made on 0.8 
and 1.2 gm. charges of prepared starch, in which the conversion prod¬ 
ucts were subjected to the action of 60 per cent alcohol, yielded results 
accounting for 100 per cent of the starch known to be present. On 
the other hand, alcohol of this strength served perfectly to coagulate 
and precipitate linseed mucilage and apple pectin. It was shown also 
that 35 per cent alcohol served well in the preliminary extraction of 
sugars and other carbohydrates that affect the results in a determination 
of starch. 
A new method of analysis, consisting of the following steps, was 
devised: (a) Preliminary extraction with 35 per cent alcohol; * 11 (b) con¬ 
version of the starch by an infusion of barley malt; (c) separation of 
mucilage or other interfering polysaccharid by its coagulation and 
precipitation in 60 per cent alcohol; (d) elimination of alcohol from 
the filtrate by evaporation and acid hydrolysis of the starch conversion 
products to dextrose; (e) defecation of the acid dextrose solution by 
phosphotungstic acid; and (f) determination of the dextrose by copper 
reduction. 
RESULTS OBTAINED WITH REVISED METHOD 
In order to test the accuracy of the method, determinations were 
made on charges containing known quantities of added starch. The 
starch used for this purpose was prepared by washing a good grade of 
cornstarch with water until the extract gave no blue color with iodin, 
washing with 95 per cent alcohol and then with ether, and finally drying 
in a vacuum oven at 65° to 70° C. 
Analysis of this prepared starch gave the following results: Starch by 
the official acid hydrolysis method, 12 average of 4 determinations, 87.62 
per cent; starch by the malt-diastase method, with the 60 per cent 
alcohol purification, average of 2 determinations, 87.19 per cent; ash, 
0.10 per cent; nitrogen by a micro-kjeldahl determination, 0.077 per 
• H. C. Gore, of the Bureau of Chemistry, showed that a heavy malt sirup formed a clear solution in 
alcohol of a concentration of more than 60 per cent. 
19 The highest concentration of starch conversion products tested was that corresponding to 1.5 
of original starch to 500 cc. of the 60 per cent alcohol. No turbidity developed overnight. In 80 per cent 
alcohol some turbidity was noticeable. ... 
11 Twenty-five per cent alcohol, being a better solvent, serves best with materials that are not impervious 
to it. 
1* This check determination was made by J. I. Palmore, of the Pood Control Laboratory, Bureau of 
Chemistry. 
