This section is from the book "Alcohol, Its Production, Properties, Chemistry, And Industrial Applications", by Charles Simmonds. Also available from Amazon: Alcohol: Its Production, Properties, Chemistry, And Industrial Applications.
The total ash may be determined on 25 c.c. of the beer, first evaporating and charring the solids over a low flame, then extracting the alkali salts with water, filtering, and completing the ignition of the carbonaceous residue. The aqueous extract is then returned to the capsule, evaporated to dryness, and the whole residue cautiously ignited.
If the chlorides are to be determined, it is well to evaporate and ignite a separate quantity of 25 c.c. or 50 c.c. after adding a little barium carbonate (05 gram for 50 c.c.), and proceed as before to obtain the aqueous extract, in which the chloride may be estimated with silver nitrate, either gravimetrically or volumetric ally.
The sulphates are also best determined on a separate quantity evaporated with addition of a little sodium hydroxide and ignited as usual. The alkali prevents loss of a little sulphuric acid, which might otherwise occur owing to the presence of acid phosphates.
Sulphites, which may be present in beer as preservatives, can be determined in terms of sulphur dioxide by distilling 250 c.c. of the sample, acidified with phosphoric acid, in a current of carbon dioxide until about 200 c.c. of distillate have passed over. The distillate containing the sulphur dioxide is allowed to drop into a flask containing a measured quantity of N/50.iodme solution, and the excess of iodine is determined with iV/50.sodium thiosul. phate solution, using starch as indicator. The carbon dioxide should not bubble through the iodine solution, or iodine will be lost. Alternatively, and rather more accurately, the distillate is received in a somewhat stronger solution of iodine (N/10 or N/20), and the sulphate formed is estimated gravimetrically as barium sulphate. Traces of sulphur dioxide, it should be remembered, may be given by the hops or other normal constituents of the beer.
An interesting quantitative study of the nitrogenous constituents of typical British beers has been made by J. S. Sharpe.1 The total nitrogen ranged from 0 039 to 0.112 per cent. Protein accounted for 13.37 per cent. of the nitrogen; amino-compounds for 25.46 per cent.; and purine nitrogen, present as uric acid and xanthine compounds, for 25.52 per cent. Traces (0007 to 0012 per cent.) of an alkaloidal oil, presumably coniine, and a small quantity of a base which was probably betaine, practically accounted for the balance of the nitrogen (2.6 per cent.).
1 Biochem. J., 1917, 11, 101.
In the United Kingdom, the quantities of beer produced by brewers for sale in the year ended 31st March, 1914, were as follows: -
Average sp. gr.