10 



DETERMINATION OF MALIC ACID. 



The use of such a screen has the additional advantage of lowering 

 the specific rotation of the uranium-malic complex somewhat and con- 

 sequently partially correcting for the normal rise in specific rotation 

 due to concentration. 



TABLE IV. Determination of factor. 



DISCUSSION OF RESULTS. 



The results which have been obtained in the application of the 

 method are tabulated in Tables V and VI, pages 11 and 12, which are 

 in the main self-explanatory. Table V contains the results of de- 

 terminations in which known amounts of malic acid were added by 

 the analyst, while the determinations recorded in Table VI were 

 made on solutions in which the amount of malic acid was unknown. 

 The percentages of invert sugar given in the second column of 

 Table V are only approximate. This accounts for the fact that in 

 some cases solutions containing the same amount of sugar and malic 

 acid show a larger difference in polarization than can be accounted 

 for by errors in reading. Stock solutions containing 5 or 10 per cent of 

 carefully weighed C. P. malic acid were made up and the percentages 

 of acid present were determined by titration against standard 

 alkali. A measured portion of the stock solution was then added to 

 a definite volume of invert-sugar solution and the mixture diluted 



