the invertase inversions to see that the rotation remains constant for 

 a few minutes. It is the writer's practice, after the invert reading is 

 obtained, to add a pinch of cane sugar to the solution and observe its 

 rotation for a few minutes; if it gradually changes, showing that the 

 cane sugar added is being inverted, one is certain that the invertase is 

 active and has accomplished a complete inversion overnight. 



TESTS OF THE INVERT A SE METHOD. 



1. Test on pure cane sugar. Direct polarization (/S), 100; invert 

 polarization, with hydrochloric acid, -33.2; consequently the per 



S' I 

 cent sugar by Herzf eld's formula, - XlOO, is 100.4. The in- 



142.7-2 



version by invertase gave /= 31.9, and the percentage by the above 

 formula with the constant 141.7 for invertase, as described before, 

 is 100.1. The polarization in all tests were made at 20 C. 



2. Test on Louisiana cane sirup. This sirup had been treated with 

 sulphur dioxid in the process of manufacture. Direct polarization 

 was 55.6, invert polarization by hydrochloric acid, 14.9, by in- 

 vertase, 13.8, giving the percentage of cane sugar by hydrochloric 

 inversion as 53.1, and by invertase inversion 52.7 per cent. 



3. Test on bagasse. S. F. Sherwood, of this Bureau, recently obtained 

 the following percentages of cane sugar in samples of Cuban bagasse, 

 using the hydrochloric acid and also the invertase methods of inversion 

 and determining the invert sugar for both methods by the change of 

 polarization and also by the increased reduction of Fehling's solution: 



Determination of cane sugar in Cuban bagasse by the hydrochloric and the invertase 

 methods. (Sherwood. ) 



These three substances, pure cane sugar, cane sirup, and bagasse, 

 show practically the same cane sugar percentage by the hydrochloric 

 acid and the invertase methods. There will now be given an example 

 of a very different type of analysis. 



4- Test on the sotol plant (Dasylirion texanum). a The soluble matter 

 from 26 grams of this plant was dissolved to 100 cc and the polarization 



interesting plant occurs in the waste dry regions of New Mexico and Texas; 

 a description of it is given in W. L. Bray's "The Vegetation of the Sotol Country in 

 Texas." (Univ. of Texas, Bui. No. 60.) 



Cir. 50. 



