84 PROVISIONAL METHODS JOB ANALYSIS OF FOODS. 



One cubic centimeter of decinormal sodium hydroxid solution is equivalent to 

 0.0075 gram tartaric acid. 



7. DETERMINATION OF VOLATILE ACIDS. 



Distill, in a current of steam, 50 cc of wine, to which a little tannin has been added 

 to prevent foaming. Heat the flask containing the sample until the liquid boils, 

 lower the flame under it and pass the steam through until 200 cc have been collected 

 in the receiver; titrate the distillate with decinormal sodium hydroxid solutic-n, 

 using phenolphthalein as indicator, and express the result as acetic acid. 



One cubic centimeter of decinormal sodium hydroxid solution is equivalent to 

 0.006 gram acetic acid. 



8. DETERMINATION OP FIXED ACIDS. 



The amount of fixed acids is ascertained by subtracting 1.25 times the volatile 

 acids from the total acids expressed as tartaric. 



9. DETERMINATION OF UNDETERMINED EXTRACT. 



The amount of undetermined extract is ascertained by subtracting the sum of the 

 glycerol, ash, protein, and fixed acids from the weight of the sugar-free extract. 



10. DETERMINATION OF SUGAR.* 

 (a) PREPARATION OF SOLUTION. 



Place 200 cc of wine in a porcelain dish, exactly neutralize with an approxi- 

 mately normal solution of sodium hydroxid, using litmus paper as indicator, and 

 evaporate to about one-fourth the original volume. Transfer to a 200-cc flask, add 

 sufficient basic lead acetate b to clarify, dilute to the mark with water, shake, and 

 filter through a ribbed filter. Transfer 100 cc of the filtrate to a flask graduated at 

 100 and 110 cc, fill to the upper mark with a saturated solution of sodium sulphate, 

 shake and filter. 



(b) POLARIZATION. 



(1) Direct. 



Polarize part of the filtrate in a 200-mm tube, in a Schmidt and Haensch polari- 

 scope, and increase the reading by one-tenth for the polariscope reading. In case 

 the reading is taken on some other instrument than the Schmidt and Haensch it 

 may be calculated by the following data: 



1 Ventzke =0.3468 angular rotation D. 



1 angular rotation D =2.8835 Ventzke. 



1 Ventzke =2.6048 Wild (sugar scale). 



1 Wild (sugar scale) =0.3840 Ventzke. 



1 Wild (sugar scale) =0.1331 angular rotation D. 



1 angular rotation D =0.7511 Wild (sugar scale) . 



1 Laurent (sugar scale) =0.2167 angular rotation D. 



1 angular rotation D =4.6154 Laurent (sugar scale). 



(2) Invert. 



In order to determine the presence or absence of sucrose it is necessary to subject 

 the sugars to inversion. The filtrate from the lead sulphate obtained in (a) may be 



'See Appendix, p. 156. 



b Prepared by boiling for half an hour 430 grains of normal lead acetate, 130 grams of litharge, and. 

 1000 cc of water. The mixture is allowed to cool and settle, when the supernatant liquid is diluted 

 to 1.25 specific gravity with recently boiled water 



