The methods of analysis used were those given in Bulletin 107, revised
(U. S. Dept. Agr., Bur. Chem.), pages 90-94, with the exception that the
determination of phosphoric acid was made by the method used in
fertilizer analysis (ibid., pp. 2-5), destroying the organic material in
the beer by digestion with strong sulphuric acid and nitric acid and
determining the phosphoric acid finally by the optional volumetric
method (ibid., p. 4). The uranium acetate method given for beers was not
used, for the reason that it was found to be exceedingly difficult to
obtain accurate results on dark-colored beers.[1]
[Footnote 1: Riley, in his report to the Association of Official
Agricultural Chemists for the year 1913, stated that the method giving
the most uniform results was that of ashing the beer with an excess of
standard calcium acetate, and that while the moist combustion method in
the hands of those familiar with it gave satisfactory results, the
various collaborators working with the method did not get as uniform
results as with the method of ashing with calcium acetate. J. Assoc.
Off. Agr. Chemists 1 (1915), 138-143.]
It was found in the estimation of dextrin by the Sachsse-Allihn method
(ibid., p. 91) that there is an error in the method of calculation of
the amount of dextrose formed from the amount of maltose in the original
beer. Instead of multiplying the amount of maltose in the original beer
by the factor 0.9, it should be multiplied by the factor 1.053, as 1
gram of anhydrous maltose yields, on hydrolysis, 1.053 grams of
dextrose. The product is the quantity which should be subtracted from
the total amount of dextrose found after hydrolysis. The extract in the
beer was determined by use of the tables of Schultz and Ostermann
(ibid., pp. 209-213). The same methods were used in the analyses of the
worts as were used in the examination of the beers.