BEEE. 91 



6. Degree of Fermentation. 



200 A 



Calculate from the formula D= in which D Is the degree of fermentation. 



B 

 A=percentage of alcohol by weight, and B the original extract. 



7. Total Acids. 



(A) Heat 20 cc of the sample to incipient boiling to liberate carbon dioxid, 

 and titrate with tenth-normal sodium hydroxid, using neutral litmus as Indi- 

 cator. Each cubic centimeter of tenth-normal alkali employed is equivalent to 

 0.009 gram of lactic acid. The number of cubic centimeters of tenth-normal 

 alkali employed in titrating 20 cc of beer is multiplied by 0.045 for the acidity 

 expressed to grams of lactic acid per 100 cc. 



(B) Calculate the cubic centimeters of tenth-normal sodium hydroxid required 

 to neutralize the acidity of 100 cc of the sample. 



8. Volatile Acids. 



(A) The volatile acid, as acetic acid, is determined by titrating 20 cc of the 

 alcoholic distillate with tenth-normal sodium hydroxid solution, using phenolph- 

 thalein as an indicator. The number of cubic centimeters of tenth-normal alkali 

 employed multiplied by 0.030 gives the acidity expressed as grams of acetic acid 



(per 100 cc. 



(B) Calculate the cubic centimeters of tenth-normal sodium hydroxid required 

 to neutralize the acidity of 100 cc of sample. 



9. Reducing Sugars. 



Dilute 25 cc of beer, free from carbon dioxid, with water to 100 cc. Deter- 

 mine the reducing sugar in 25 cc of this solution as directed on page 42, under 

 " VI. General Methods," the solution being boiled four minutes instead of two. 

 Express the result in terms of maltose equivalent to copper reduced according to 

 Ipe table given on page 47. 



10. Dextrin. 



(a) SACHSSE-ALLIHN METHOD. 



Dilute 50 cc of beer and 15 cc of hydrochloric acid, specific gravity 1.25, to 

 I BOO cc, attach to a reflux condenser, and keep in a boiling-water bath for two 

 [pours. Employ Sachsse's method for the hydrolization of starch and determine 

 [pextrose according to Allihn. ("VI. General Methods," pp. 49 and 53.) The 

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

 jaivided 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 bee* 

 |md multiply the remainder by 0.9, the result being the percentage of dextrin in 

 original wort. 



(b) OPTIONAL METHOD. 



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

 reen its optical activity and that of maltose. 



A / TIC \/ Q 1 ^ 



D= ii 6 wnen D=dextrin, in grams per 100 cc, A=total rotation in degrees 



fentzke in 200 mm tube, and M percentage of maltose as determined gravi- 

 itrically. 



87404 Bull. 10709 8 



