92 METHODS OF ANALYSIS. 



11. Direct Polarization. 



Read the polarization of the original sample in degrees Ventzke in a 200 mm 

 tube. If the beer is turbid, clarify by shaking with alumina cream. 



12. Invert Polarization. 



To 10 cc of the beer in a small flask add 1 cc of concentrated hydrochloric 

 acid, invert by slowly heating to 68 C., cool, polarize in a 200 mm tube, and 

 increase the reading one-tenth to allow for dilution. 



13. Glycerol. 



Proceed as directed on page 83 under " XIII. Wine." The milk of lime is 

 added during evaporation after the carbon dioxid has been expelled. It is 

 advisable that the filtrate after being evaporated to a sirupy consistency be 

 treated again with 5 cc of absolute alcohol and 2 portions of 7.5 cc each of 

 absolute ether. If clear, continue as directed. If not clear, it is necessary to 

 repeat the treatment with lime. 



14. Ash. 



Evaporate 25 cc of the sample to dryness, and determine according to method 

 given under " VI. General Methods," page 38. 



15. Phosphoric Acid. 



Measure out 50 cc of the orignal beer, free from carbonic acid, into a small 

 beaker. Add 5 cc of an acid solution of sodium acetate and heat to boiling. 

 Run in with a burette, standard uranium solution, 0.5 cc at a time, testing each 

 time until a drop of the beer when placed on a white plate colors a drop of ! 

 potassium ferrocyanid slightly brown. The number of cubic centimeters of the 

 uranium-acetate solution necessary, multiplied by 0.01 gives the grams per 100 

 cc of phosphoric acid in the beer. If the beer is very dark, employ the official 

 gravimetric or volumetric method, using the residue obtained in the determina- 

 tion of the ash. ("I. Fertilizers," pp. 1 and 4.) 



16. Protein. 



Evaporate 25 cc of the original beer, to which has been added a small amount 

 of tannin to prevent frothing, and proceed according to the Kjeldahl or Gunning 

 method for the determination of nitrogen and multiply the result by 

 ("I. Fertilizers," p. 5.) 



17. Carbon Dioxid. 

 (a) BOTTLED GOODS. 



Pierce the cork with a champagne tap.<* Connect with a suitable absorption 

 apparatus, placing an Erlenmeyer flask between the bottle and absorption tubes 



Hassall, Food : Its Adulterations and Methods for their Detection, 1876, p. G68. 

 Used by Wiley (Amer. Chem. J., 1886. 8: 200) in the examination of koumiss, and by 

 Crampton in the examination of beer. Crampton found it necessary to regrind the 

 cocks and ream off the thread, leaving a smooth tube. (U. S. Dept. Agr., Division of 

 Chemistry, Bui. 13, pt. 3, p. 294.) 



