15 



10. DEXTRIN. 

 (A) SACHSSE-ALLIHN METHOD. 



Employ Sachsse's method for the hydrolization of starch and determine dextrose, 

 according to Allihn, as follows: 



Fifty cc of beer and 15 cc of hydrochloric acid, specific gravity 1.125, are diluted 

 to 200 cc, attached to a reflux condenser and kept in a boiling water bath for two 

 hours. Neutralize with caustic soda and dilute to 250 cc, or 300 cc in a beer with 

 high extract. Add 25 cc of the solution to the boiling Fehling solution and boil two 

 minutes. Multiply the oxid of copper found by 0.8 to obtain the corresponding 

 amount of copper and refer to Allihn's dextrose table (Table VIII, p. 143, Bui. 65). 

 The amount of dextrose thus found multiplied by 20 (or 24 if diluted to 300 cc) and 

 divided by the specific gravity equals the dextrose in the original beer. From this 

 figure subtract 95 per cent of the amount of maltose in the original beer and multiply 

 the remainder by 0.9, the result being the percentage of dextrin in the original wort. 



(B) OPTIONAL METHOD. 



Dextrin may be determined by the following method, based on the difference 

 between its optical activity and that of maltose. 



D = A ~( Mx8 ' 1 lwhen D=dextrin, in grams per 100 cc, A=total rotation in 



11.6 



degrees Ventzke in 200 mm tube, and M= percentage of maltose as determined 

 gravimetrically. 



11. DIRECT POLARIZATION. 



Bead 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 62, Bulletin 65. 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 treat again as below. 



14. ASH. 



Evaporate 25 cc of the sample to dryness, ignite at low redness until thoroughly 

 charred, place in a muffle and continue the ignition until ash is white. Leaching is 

 rarely necessary. 



15. PHOSPHORIC ACID. 



Measure out 50 cc of the original 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 determination of the ash. 



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 Kjeldahl or Gunning method 

 for the determination of nitrogen and multiply the result by 6.25. 



[dr. 33] 



