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acid) gave, by reduction in hydrogen, 48.26 per cent. iron, showing complete reduction of all the iron but the small amount present in a combination insoluble in hydrochloric acid. This method is not recommended for geueral use, but is given merely as an illustration of the widely various uses to which the crucible may be put. I t is, however, not adapted for those organic combustions in which condensible decomposition products are formed. These condense in the cooler upper part of the crucible where they are beyond reach of the temperature necessary to burn them. Probably by mixing such organic compounds with suitable oxidizing material, such combustions might be successfully made, but this is a field that has not yet been investigated My last combustion apparatus w a s made for me by the Baker and Adamson Chemical Co., of Easton, P a . , who also furnished me with a reliable quality of pure rubber hands. [ CONTRIBUTIOXS FROM THE CHEXICAL LABORATORY O F THE M E N T O F AGRICULTURE, NO.
c.s.DEPART-
34.1
T H E INFIJJENCE OF TEMPERATURE ON T H E SPECIFIC ROTATION OF SUCROSE A N D IlETHOD OF CORRECTING READINGS OF COMPENSATING POLARISCOPES T H E R EFOR.’ B Y I I X R V E S \%’,
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Keceived X a r i h 9 , IS&
T
HE influence of temperature on the specific rotation of
sucrose has been mentioned by several authors. A partial r4suink of the literature on the subject is given by von Lippmann.’ A more detailed discussion of the subject is given by S a c h ~ .A ~ rather full abstract of previous papers on the subject is given by Sachs, who strangely, however, fails to mention the paper of Andrews on this subject. T h e early writers with the exception of Dubrunfaut‘ seem to be unanimously of the opinion that the temperature exerts no notable influence on specific rotation. This is the doctrine announced by Tuchschmidt’ and 1 Read before the American Chemical Society and Section C, of the American Association for the advancement of Science, at Boston Meeting, August, 1898. and before the Third International Cougress of Applied Chemistry, Vienna, August, 1998. 2 Chemie dev Zuckdmrten, Edition r895! page 672. a Ztschv. Riibenruckrrind., 46, 264. 4 J . p r a k t . Chem., 1 8 , IO. 5 Zfschr. RQbenzuckevind., (r870), 649.
S P E C I F I C ROTATION O F SUCROSE,
ETC.
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Mitscherlich.' Sachs also cites the experiments of Wachtel,' who explained the difference in polarization under the influence of temperature by ascribing it to the expansion of the quartz plates of the compensating polariscopes used. This explanation is evidently insufficient, and, as will appear further on, erroneous. Petrucci and S a c h ~ in , ~ 1889, also observed differences in polarization, due to temperature, and these observations were corroborated by Wartze.' T h e experiments of Sachs were conducted by making the sugar solution at a given temperature and then polarizing it at other temperatures, and also by making up the sugar solution at the same temperature at which it was polarized. As a result of his investigations, he concludes that a solution of practically pure sugar, made up at 17.j0, and polarized at 17.5', will show a decreased polarization of 0.20' Ventzke, when made up a t 25' and polarized at 2j'. T h e causes of variation in polarizations in the trade were considered in a convention of technical chemists held in Berlin in 1895.6 I n the United States the first corrections which were employed for variations in polarizations due to temperature were those ascertained by the Office of Weights and Measures of the United States Coast and Geodetic Survey in 1890, and adopted by the commission appointed by the Secretary of the Treasury to prepare regulations for use in the Bureau of Internal Revenue of the Treasury Department. T h e total correction due to variations in temperature for each degree C., as prescribed by the regulations, was 0.02g3' Ventzke for a sugar polarizing 100' Ventzke. This correction was uniformly employed in the Bureau of Internal Revenue, in polarizations for determining the amount of bounty to be paid on domestic sugar in the United States, during the whole time in which the act granting such bounty was in force. I t appears, therefore, that the first practical application of a correction for variations in temperature in sugar polarizations was applied in the United States. 1 Bevl.
Acad. Bey.. ( 2 8 4 2 ) , 150. Organ des Cenfral-Verein, Wien 2878. 42. 8 Bull. Assoc. Belge Chim., 15 Febr., 2889, IIZ. 4 Deutsche Zuckerind., 20 April, 2889. 6 Zfschr. des Veveinsf u r Ritdenruckerind., (2895). I, 73. 2
57 0
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A painstaking study of the influence of teniperature on the polarization of cane-sugar was made by Andrews.' As a result of the investigations he deduced the following formula to express the influence of temperature on specific rotation : [a]: = [ a ] ~ - 0 . 0 1 1 4 ( f - 2 0 ) . ~ If 66.j o be taken as the mean value for [a]: the coefficient of change per degree C. is 0 . 0 0 0 1 7 1 , which ~ is somewhat smaller than that obtained by Dubrunfaut ; namely, 0.000232. T h e formula for calculation used by Andrews was
i n which a = angle observed, i n degrees ; I = length of tube, in decimeters ; 3 = percentage of sugar, by weight iz vacuo. d= specific gravity of the solution at temperature of observation, water at 4' C. being unity. Dividing the total difference in rotation for different temperatures by the number of degrees of difference in the two sets of experiments conducted by Andrews, we have the following as the variation in the rotation for each degree C. in the two sets of experiments : Difference per degree in t h e first set ................. 0.0106 i'
