228 



ture upon the rotation of the levulose begins to lower the theoretical sucrose correc- 

 tion, until at a point usually about 80 to 86 the two influences that of the tempera- 

 ture upon the levulose and other impurities and that of the temperature upon the 

 sucrose and quartz wedges of the instrument counterbalance one another. Two 

 chemists polarizing such a sugar, one working at 30 C. and one working at 20 C., 

 other conditions being equal, will obtain concordant and correct readings; the appli- 

 cation of the theoretical sucrose correction would place the observation of the chemist 

 working at 3Q C., 0.25 V. too high. 



Below 80 the effect of increase in temperature is usually to elevate rather than 

 diminish the reading, this influence becoming more and more pronounced in the 

 massecuites and molasses; the levulose correction more than counterbalances the 

 theoretical one due to sucrose. Every chemist knows how pronounced this influence 

 is on the polarization of sirups and molasses, how the simple handling of the observa- 

 tion tubes will increase the readings. It is the same with low-grade sugars which 

 consist simply of sucrose crystals contaminated with varying amounts of molasses. 

 When such sugars are polarized above 20 C. a correction would have to be subtracted 

 to secure the reading that would be obtained under standard conditions. To add a 

 correction, as required by a sucrose correction formula, would manifestly only further 

 increase the error of observation. 



The solution of the temperature question then resolves itself simply into this: If 

 we are to make temperature corrections in the polarizations of commercial products, 

 we must correct for variations in the specific rotation of all the ingredients therein 

 present. If it is impossible to do this, no temperature corrections at all should be 

 applied; instead of this we should strive to make our polarizations as nearly as possible 

 under standard conditions. Custom-house laboratories, arbitration laboratories, and 

 all other laboratories, upon the results of which great interests are involved, should be 

 equipped with cooling and warming apparatus for maintaining a constant uniform 

 standard temperature. The great testing laboratories of Germany are so provided 

 and similar institutions in this country should do as much. For chemists who are 

 unable to provide themselves with this equipment much can be done by moving 

 the laboratory to cooler quarters, as from a hot upper room to a cool basement. By 

 such a change the New York Sugar Trade Laboratory has lowered the temperature 

 of testing from 25 C. to 21.5 C. in hot weather. 



The services rendered to science by the researches of the many chemists who have 

 investigated the influence of temperature upon the specific rotation of sucrose are 

 great; the results of their labors are lasting and will stand the test of time. The appli- 

 cation, however, of what they have established for pure sucrose to the polarization 

 of all grades of saccharine products is a misapplication. It is a great mistake. It 

 will increase rather than diminish the errors between many of the sacchari metric 

 observations of different analysts and is bound to work great injustice when applied 

 commercially. 



A paper on the influence of glycerin, acetanilid, and certain other 

 drugs in the estimation of alcohol by L. E. Warren and H. C. Fuller 

 of the Division of Drugs, Bureau of Chemistry, was presented by 

 Mr. Warren. This work, bearing especially upon the drug investiga- 

 tions, has been printed elsewhere for greater accessibility. 



The associate referee presented a lengthy paper by S. H. Baer on 

 the colorimetric method for the determination of citral, dealing 

 largely with the chemistry of that substance. The portions on 

 criticisms of the method are reported in abstract. 



oAmer. J. Pharm., 1909, 81: 66. 



