XVIII] BEERS 251 



1 8 PROTEIN.-OFFICIAL. 



Measure, at 20°C., 25 cc. of the carbon dioxid-free beer into a Kjeldahl digestion 

 flask, add a small amount of tannin to prcvcMit frothing, evaporate to dryness, de- 

 termine nitrogen as directed under I, 18, 21 or 23, multiply the result by 6.25 and 

 calculate the percentage of protein, 



1 9 PRESERVATIVES.-TENTATIVE. 

 Proceed as directed under X. 



20 COLORING MATTERS.— TENTATIVE. 

 Proceed as directed under XI. 



21 METALS.-TENTATIVE. 



Proceed as directed under XII. 



