September 24, 1920] 



SCIENCE 



299 



I The conductivity titration of chrome liguors: 

 Aethub W. Thomas and S. B. Foster. 



Physico-colloidal interpretations of the tanning 

 and tawing procedures: I. Newton Kugelmass. 



The currying of leather for belting: Edward E. 

 Makbaker. 



Chemical worTc in the tannery: Louis E. Levi. 



sugar section 

 0. A. Brownej chairman 

 Fred. J. Bates, secretary 

 Chemical control in the heet sugar industry: 



S. J. OSBOEN. 



The testing of saiccharimeters iy means of the 

 telescopic control tube: C. A. Browne. Uses of the 

 control tube are described (1) for determining the 

 errors of saccharimeter scales, (2) for comparing 

 scales, (3) for determining sensibility of saecliari- 

 meters, (4) for testing ability to polarize accurately, 

 (5) for determining influence of personal equation. 

 The maximum scale error on good instruments was 

 found not to exceed 0.04° v. The probable error 

 of a single reading on a German saccharimeter 

 was ±'.05 and on a Bohemian ± .03 or an aver- 

 age of lb .04. Personal equation may produce a 

 constant one way difference of it .04 between 

 different observers. Eeversing the optical con- 

 struction of saeeharimeters was found to reverse 

 the order of personal equation. Disputes about 

 the values of normal weights no doubt result 

 partly from personal equation. 



Observations upon the use of different types of 

 saeeharimeters : C. A. Browne. Observations are 

 given of the good and bad features noted in the 

 practical use of saeeharimeters of American, Eng- 

 lish, French, German and Bohemian manufacture. 

 The advantages and disadvantages are presented 

 of the open and closed construction types of instru- 

 ments, of the various forms of polarizers, of dif- 

 ferent kinds of saccharimeter scales, and their 

 comparative accuracy, and of differences in meth- 

 ods of illumination, trough construction and other 

 details. As a result of his inspection the author 

 believes the outlook for the manufacture of ac- 

 curate saeeharimeters in. countries outside of cen- 

 tral Europe is most encouraging. 



The filteration of sugar-juices and syrups: 

 Walter L. Jordan. 



The clarification of cane juice without chemical 

 treatment: F. W. Zerban. Previous investigators 

 have found that nearly three fourths of the im- 

 purities which are removed by treatment of cane 



juice with heat and lime, can be taken out by 

 filtration in the cold, and that therefore the 

 chemical effect of the lime treatment plays only 

 a small part in clarification with this process. It 

 was also shown by the same investigators that the 

 greater part of these impurities exist in the juice 

 in colloidal form. Conclusions based on these 

 facts are further developed in this paper, and it 

 is pointed out that the effectiveness of the vari- 

 ous chemical clarification methods at present in 

 use may in their broad outlines be explained by 

 colloid-chemical considerations. It is very prob- 

 able that surface energy, and particularly adsorp- 

 tion, is the principal factor in these classification 

 processes. It follows from these theoretical con- 

 siderations that cane juice clarification may be 

 brought about without the use of any chemicals 

 whatever, but simply by the use of efficient ad- 

 sorbents. Laboratory and factory tests have given 

 strong evidence that this is actually the case, and 

 it was found that in comparison with the sulfita- 

 tion process, at least the same quantity of first 

 sugar of greatly superior quality can be made by 

 clarification with one half per cent. FUter-Cel, fol- 

 lowed by treatment with 1 per cent. Norit, and 

 filtering the juice in both cases, which is easily 

 and rapidly done. The first molasses is so very 

 light in color that the recovery of high-grade sugar 

 can probably be materially increased, still leav- 

 ing a molasses of higher market value than that 

 made by the usual plantation methods. 



The Eess-Ives tint-photometer and its use with 

 raw sugars: George P. Meade and Joseph B. 

 Harris. The scale readings of the Hess-Ives Tint- 

 Photometer are meaningless ia themselves as they 

 do not express directly the relative amounts of 

 color. It was found that the scale readings for 

 solutions containing 1, 2, 3, 4, etc. units of ma- 

 terial run in powers of the reading for one unit, 

 considering the scale readings as decimal frac- 

 tions. This is due to the mechanical make-up of 

 the instrument, and is true no matter which color 

 screen or what class of material is used. Ex- 

 pressed algebraically, this relationship between the 

 scale readings and the amounts of color becomes 

 y = K'', where y is any scale reading, K is the 

 reading for one unit of material, and x is the 

 number of units of material required to give the 

 scale reading y. By means of this equation solved 

 for X the color of two materials may be compared, 

 given scale readings for equal quantities; or all 

 scale readings may be compared to a standard. 

 To avoid the repeated calcidations, a table has 



