The positive detection of the presence of artificial substitutes for malt in beer is a matter of considerable difficulty. According to Haarstick, a large proportion of commercial glucose contains a substance termed _amylin_, which exerts a strong dextro-rotary effect upon polarised light, but is not destroyed by fermentation, and upon these facts is based a process for the identification of starch-sugar in beer. It is executed by evaporating 1 litre of the sample to the consistency of a syrup and separating the dextrine present by the gradual addition of 95 per cent. alcohol.[77] After standing at rest for several hours the liquid is filtered, the greater portion of the alcohol removed from the filtrate by distillation, and the residual fluid evaporated to dryness over the water-bath. The solid residue is then diluted to about a litre, yeast added, and the sugar present decomposed by allowing fermentation to take place for three or four days, at a temperature of 20°. It was found that, under these conditions, pure beer afforded a solution which was optically inactive when examined by the polariscope, while beer prepared from artificial glucose gave a solution possessing decided dextro-rotary power. The use of rice and glucose in the manufacture of beer is also indicated when there is a deficiency in the proportion of phosphoric acid in the ash, and of the extract, which applies, although to a somewhat less extent, if wheat or corn meal has been substituted for barley malt. The following conclusions were reached by a commission of chemists appointed in Germany to determine standards for beer:--A fixed relation between the quantity of alcohol and extract in beer does not invariably exist. As a rule in Bavarian and lager beer, for 1 part by weight of alcohol a maximum of 2 parts and a minimum of 1·5 parts of extract should be present. In case malt has been replaced by glucose, or other non-nitrogenous substances, the percentage of nitrogen in the extract will fall below 0·65. The acidity should not exceed 3 c.c. of normal alkali solution for 100 c.c. of beer. The ash should not exceed 0·3 per cent. The maximum proportion of glycerine should not exceed 0·25 per cent. For clarification, the following means are permissible: Filtration, the use of shavings, etc., and of isinglass or other forms of gelatine; for preservation, carbonic acid gas, and salicylic acid may be employed--the latter, however, only in beer which is intended for exportation to countries where its use is not prohibited.