1897.] PUBLIC DOCUMENT — No. 33. 93 



Recognizing the comparatively few fodder plants and seeds 

 tliat had been tested for galactan, we thought it would prove 

 interesting to make a quantitative estimation of the amount 

 of the substance present in all the more important feed stuffs. 

 While the method employed by Schulze, namely, the invert- 

 ing of the galactan with dilute mineral acid and allowing the 

 resulting sugar to crystallize out, is of course a sure proof 

 of the presence of galactose, if properly identified, it does 

 not admit of a quantitative estimation of the sugar. We 

 therefore had recourse to the indirect method of estimating 

 the mucic acid, as a measure of the quantity of galactose 

 present. Scheele * was the first to recognize that by the 

 oxidation of milk sugar, mucic acid resulted. Pasteur f 

 found that it was the galactose of the milk sugar that yielded 

 mucic acid. Tollens and Kent,| after numerous experiments, 

 proposed the following method for obtaining the largest 

 amount of mucic acid both from milk sugar and from galac- 

 tose. They evaporated 100 grammes of miik sugar with 

 1,200 c.c. of nitric acid of 1.15 specific gravity in a water 

 Imth to one-third of its volume, allowed the solution to stand 

 twenty-four hours for the mucic acid to crystallize out, then 

 filtered onto a tared filter and dried and weighed it. This 

 method yielded 37 to 40 per cent, of mucic acid. When 

 pure galactose was used, a double quantity — 74-77 per 

 cent. — was obtained. § Rischbieth, Creydt, Hadecke and 

 Tollens still further perfected the method, and used it in 

 ascertaining the galactan in a variety of substances. This 

 perfected method we have used with but slight modifications 

 in the estimation of galactan in the substances which follow. 



Method. — Three grammes of the substance were brought 

 into a beaker about 5.5 cm. in diameter and 7 cm. deep, 

 together with 60 c.c. of nitric acid of 1.15 specific gravity, 

 and the solution evaporated to exactly one-third of its volume 

 in a water bath at a temperature of 94 to 96 degrees C. After 

 standing twenty-four hours, 10 cc of water are added to the 

 precipitate, and it is allowed to stand another twenty-four 



* Opuscula chemica et physica, Leipsig, 1789, p. 111. 



t Comp. rend. 42, p. 347. 



t Ann. Chem. 227, p. 221. 



\ Landw. Versuchs-Stationeu 39, p. 401. 



