I N D U S T R I A L A N D ENGINEERING CHEMIXTRY
56
there is only slight inversion, if any, but below.which inversion becomes definitely apparent. In the experiments on boiling sulfur-lime sirup to massecuite, also reported in Table IV, no inversion occurred, even when sirup of pH value as low as 6.0 was used. I n TableV two experiments are recorded in which sulfur-lime sirup at approximately 50" Brix was boiled at atmospheric pressure
In boiling sirup to massecuite the acidity is greater than that of the juice from which the sirup is derived, although, of course, the temperature is lower than during defecation. If boiling raw sugar sirup of pH 6.7 measured a t 15" Brix, corresponding to pH 6.35 at 50" Brix, gives results indicative of inversion, it is obviously not necessary for the purpose of this investigation to study the defecation of juice of
TABLEV-RESULTS OF BRUSHPAN
MATERIAL Sirup original Sirup: heated Sirup, original Sirup, heated
Colorimetric PH 6.80 6.60
5.95 5.90
Acidity (cc. 0.1 N NaOH per 10 cc. of sample a t 15' Brix)
Brix by hydrometer
0.55 0.62 1.45 1.25
55.20 66.50 56.68 56.92
EXPERIMENTS (SULFUR-LIME SIRUP)
Direct polarization
Solids by drying
Sucrose by invertase method
v.
% 53.42 54.80 55.09 54.99
Vol. 17, No. 1
%
40.05 41,22 41.15 40.61
41,81 43,OO 43.05 42.46
Glucose
%
Glucose ratio
7.268 7.427 7.579 8.255
17.371 17.272 17.605 19,442
ADvarent phrity
True purity
72.55 72.96 72.60 71.35
78,26
%
%
7s.47 78.14 77.21
TABLE VI-BOILING 60 PURITYMOLASSES BLANK MATERIAL Molasses Massecuite
Colorimetric PH
5.90
...
Temperature in crystallizer
Acidity (cc. 0.1 N NaOH)
Brix by hydrometer
Solids by drying
%
Direct polarization
Sucrose bv invertasemethod
Glucose
31.55 54.73
33.81 57.55
7.12 12.05
... 54.44 50.79 ... 91.22 85.82 After 24 hours 53.5' C. 2: : ~ $:: ~ ~ After 4 days, 35.0°C.
v.
for 15 minutes, and subsequently kept on the steam bath for 4 hours to duplicate approximately the practice of "cleaning" the sirup in a brush-pan in those factories operating to produce first sugar and a high grade of first molasses. No inversion occurred when the pH value of the sirup was 6.8 and the titrated acidity 0.45, whereas, when the pH of the sirup was 5.95 and the titrated acidity 1.45, the increase in glucose ratio and decrease in true purity clearly indicated appreciable in yersion. Table VI gives the results of an experiment on boiling molasses blank and then plwing it in a crystallizer. The pH value of this material, measured a t 15" Brix, was 5.9, which is as low as in any samples of molasses resulting from the sugar boiling experiments in which no inversion occurred. The close agreement between both the glucose ratio and true purity for molasses and the resulting massecuite indicates that no detectable inversion occurred during this experiment. Whenever the quinhydrone electrode was used to determine the pH value of samples of sirup directly, without diluting below 40"Brix, the pH value found was always lower than that for the same sample after dilution to 15" Brix. A variation from pH 6.36 for sirup a t 46" Brix to pH 6.61 for the same sirup a t 15" Brix represents a typical difference. This variation probably represents the net result of differences in acid concentration and dissociation and likewise of hydrogenion activity, since the volume concentration of both acid and sucrose is greater a t the higher Brix. This relation should be kept in mind in factory procedures during which water is progressively evaporated.
%
%
Glucose ratio
Apparent purity
21,059 20.937
%
57 I95 BO. 00
True purity
%
66.57 67.OR
such initial pH that it will yield sirup of the p H value mentioned. It would seem rather that the initial pH value of the juice should be such that when this same juice is evaporated to sirup, the sirup can be boiled to massecuite without inversion. Reasoning along this line, the data obtained indicate that, in defecating juice for raw sugar manufacture, the inital pH at which it is safe to carry the juice lies between 7.0 and 8.0;'o in other words, a t such a point that this juice, when evaporated to sirup, will possess a pH (measured at 15" Brix) lying between 6.7 and 7.0. I n the sulfitation process, by which direct consumption sugar is produced, it is indicated that a lower pH and correspondingly higher titrated acidity may be safely carried. The sulfites present in these sugarhouse liquors apparently retard the progressive increase in acidity by the decomposition of glucose, and may also possess a specific inhibiting property in the inversion of sucrose. Investigation of the specific influence of sulfites on p H measurement (both colorimetric and electrometric) is required for fuller explanation of this matter.
.............. A selected bibliography of literature on the inversion of sucrose and the determination of hydrogen ion has been prepared by the authors, who will be glad to furnish copies upon request. Space does not permit publication of this bibliography in connection with this article. 10
This is in substantial agreement with McAllep's conclusions, Louisi-
ana Plantev, 73, 114 (1924).
Work of Bureau of Mines Discussed in Annual Report Accidents in the coal mines of the United States continue a t a f a r too frequent rate, according to the annual report of the Bureau of Mines. Efforts have been made to increase safety in mining by the development of international cooperation with the Mines Department of Great Britain, and an extensive campaign for the adoption of rock dusting as a preventive of disastrous explosions in bituminous coal mines.
A lignite carbonizer designed by the bureau should result in the ultimate solution of the tremendously important problem of economic utilization of the lignites of the Northwest, which comprise nearly one-third of our total solid fuel resources. The use of cooling systems in vapor-tight tanks in which crude oil is stored should check evaporation losses of gasoline, which
amount annually to 3 or 4 per cept of the stocks accumulated during the winter season, and whose value runs into millions of dollars. A laboratory for radium research has been established in Washington. Important fuel economies in the operation of industrial kilns manufacturing brick, tile, and other heavy clay products have been made possible by a study of the burning problems of such kilns. At the request of the Commission of Gold and Silver Inquiry of the United States Senate, a study of new uses for silver has been undertaken. The purpose of the study is to increase the demand for the metal, and thereby aid the western silver mining industry, which has for several years faced unfavorable economic conditions.
