INDliXTRIAL A N D ENGINEERING CHEMISTRY
854
Conclusion
Spectrophotometric analysis of sugar products reveals certain facts regarding decolorization by char which ordinary colorimetric methods have never explained. The method of Peters and Phelps is based on rational principles, and allows colorimetric comparisons between different types of sugar products having different optical centers of gravity. This is especially advantageous when comparing original with decolorized sugar products, as it is possible to follow the selective properties of the char a t the same time. It cannot be stated definitely that bone char always has more difficulty in removing what appears to the eye as the red coloring matter, or that the gray or green matter is always selectively
Vol. 18, Xo. 8
removed. The selectivity may be in either the blue or red end of the product’s absorption spectrum, depending upon the nature of the coloring matter present and the relative proportions of the different general types of coloring matter present. In refinery practice intelligent use of spectrophotometric color determinations is an invaluable aid to the technologist in his efforts to locate and eliminate the imperfectly understood and empirical factors in refinery operation. As he proceeds further in his investigations and approaches the ultimate solution of the majority of his problems, he finds that the chief cause of operating difficulties is unsatisfactory raw sugars.
Action of Sodium and Magnesium Sulfates on Portland Cement’’z By G. R. Shelton UNIVERSITY OF SASKATCHEWAN, SASKATOON, CANADA
HE analysis of the coml i m e were present. These After having determined the action of sulfate solumercial cement is given results are in agreement with tions on the separate compounds found in Portland in the first paper of the work done at the Geocement clinker and also on calcium aluminates,* exphysical Laboratory6 and a t this ~ e r i e s . ~The white Portperiments were made using the same sulfate solutions t h e B u r e a u of Standards,6 land cement was made in this with a commercial and a white Portland cement. which is being questioned a t l a b o r a t o r y from alumina, The object of the present investigation was to deterpresent in studies made by white marble, and flint, mixed mine the difference in sulfate action on Portland ceDyckerhoff and Nacken.’ so that the resulting clinker ment clinker and on its compounds taken separately. The tests with solutions of would have the same percentsodium and magnesium sulage of CaO, A1203, and Si02 as the mean percentages of these oxides in analyses of a number of fates were made in small stoppered tubes, as described in commercial cements. Three heat treatments with intermedi- similar tests on the constituents of Portland cement and ate grinding and sieving were necessary to give a homogeneous also on calcium aluminate.3 The sulfate solutions were in the following molar concentraproduct. To prevent contamination of the mixture it was molded in the form of a hollow cylinder 15 em. high and 12 cm. tions: 0.05, 0.1, 0.2, 0.4, 0.8. The mixtures contained 0.08 in diameter, which was placed on a magnesite disk in the fur- gram of clinker and 5 cc. of the sulfate solution. Before presenting the data obtained in the present investiganace, the bottom of the cylinder being chipped off after each firing. The temperature of the furnace was read by means of tion, a brief summary will be given of the results obtained a Thwing optical pyrometer sighted on the bottom of an alun- with mixtures of sulfate solutions and each of the respective dum tube which projected into the furnace for about 5 em. pure constituents. and almost touched the cylinder. The maximum temperaCrystalline Cements and Sodium Sulfate ture attained was 1500’ C. No gypsum was added.
T
Analysis of Clinker
Loss on ignition Silica (SiOz) Alumina (A120a) Ferric oxide (FezOa) Lime (CaO) Magnesia (MgO)
Per cent 0.30 24.01 9.05 0.29 66.14 0.36
Microscopic examination showed irregular-shaped grains, which between crossed nicols revealed the presence of bright crystalline fragments, surrounded and held together by an isotropic substance, The largest grains gave a positive interference figure, and had refractive indices of 1.735 and 1.715, proving them to be p-dicalcium silicate. Other grains, showing a gray interference color, negative optical figure with refractive index 1.715, were tricalcium silicate. The isotropic substance had a refractive index of 1.710 and was tricalcium aluminate. KO 5:3 calcium aluminate or free Received February 23, 1926. This work was done under the auspices of a research committee of the Engineering Institute of Canada with the financial support of the Research Council of Canada, the Canada Cement Co., the Canadian Pacific Railway, and the three Prairie Provinces of Canada. 8 THISJOURNAL, 17, 589, 1267 (1925). 4 I b i d . , 17, 467 (1925). I
2
SUMMARY OF PREVIOUS RESULTSWITH PURECONSTITCENTS Pure constituents Reaction products 3 CaO Ah03 Gel, sulfoaluminate crystals, and in 0.035 M solution, hydrated 3CaO.Alz03 crystals 3 CaO.Si0a Gypsum and gel surrounding original grains, which remained unchanged in the 0.035 and 0.14 M solutions for about 2 months 8-2 CaO.SiOz Gypsum and original crystalline grains covered with gel in all the solutions; no change after 2 months
WHITEPORTLAND CEMENT-The results were very similar to those obtained by the action of these solutions of the pure crystalline tricalcium aluminate, the only crystalline products being the needles of tricalcium sulfoaluminate. No hydrated tricalcium aluminate crystals were noted in the 0.5 -Wsolution, nor was gypsum found in any of the mixtures. Original crystalline silicate grains were covered with layers of gel, but the centers could be detected between crossed nicols. These centers disappeared after 5 weeks. COMMERCIAL PORTLAKD CEMEN?LCIYSta1S Of SUlfOalUminate were found in all the mixtures, and gypsum in all except the 0.05 and 0.1 M solutions. The crystalline centers, con6
6
7
Shepherd and Rankin, THISJOURNAL, 3, 211 (1911). Concrete-Cement i l g e , 2, 3 (1913). Zenzent, 14, 174, 419 (1925).
taming fragiiientb of the oiiginal sdioates present in the inases of gel, disappeared rapidly, nolie hemg present aftcr tlie first
uwk. Crystalline Cements and Magnesium Sulfate
formed from the gypsum added to the ground cement. Mixtures were made using 1 cc. of cement suspension and 5 cc. of the sodium sulfate solutions. Crystah of gypsum were found in all of the mixtures and the fine needles of sulfoaluminate remained unchanged. Layers of gel wore formed around the crystals of hydrated lime, the latter disappearing entirely in 5 days. Crystal8 of hydrated tricalcium aluminate rapidly disappeared so that only traces were found after 9 days. The amorphous mass- w ~ r ebrownish in color and instead of remaining as flakes of clear gel became very granular. Hydrated Cements and Magnesium Sulfate S,(lbZMIRY 0x8
U'HLTEC.eut-xT-Renction products were the same as obtained in previous tests with the pure constituents except that no siilfoaluminate crystals were formed in the 0.05 M solution. The crystalline centers in gelatinous masses disappeared aft,er 6 weeks, which was greater than the time noted with m r e tricalcium silicate hut less than that with the dicalciurn silicate. CO?~~MEKCIAI, CExmT--Iteaction products were the same as t.hose formed with sodium siiliatc except that no sulfaaluminate was present.
PxBImUs RBBULT5 w r n t €IY"R*TBD
Ilvdreted ronafitueots
3 CaO.AI*Oz 3 ca~.SiO* 8-2 CaOSiO.
PUXS
cowurruetrrs
Reaction nioducts Gypsum, rniorphouf Mg(OH)n: crystals of hydrated a CaO.AbO1 diiappcared after 4 days Gypsum and grains of Ms(ON)% no .mystale of Ca(Ollh after 10 days; amorphous g r a ~ mmfained original shape G y p s u m .Mg(OH), pirtiele~;no erystaliinc centers in pa&lly hydrated g r a m after 4 weeks
T ~ H I T E CEmm-The presence of gypsum crystals was noted immediately aftor mixtures were made. The crystals of hydrated lime were covered with grainy masses and
Hydrated Cements and Sodium Sulfate Solutions
grains
H~uitn'Shio7% HIT= CEMEN'r-The hydra prepared by sliaking 25 grains of finely powdered clinker v;ith 30 cc water till all hut a tracc of the original crystalline e r a i n s h a d disnn-
F ~ t-F?ydrated s ~ ~ ~Commercial Cement in 0.08 M M*,SO& Shewine. 6 y p y u m Rovnded Grains of Gel. a n d a Large Hkieraaonal Lrystal of Hydrated Lime Parfly Covered w i t h Granular Amorphous Matter a n d Clear=Gal.
x
100
drated tricaloium aliiminato, and large ciystah of hydrated limr. illixtures wcrc made using 1 cc. of thii suspension with 5 rr of the sulfate solutions The crystali of lime w e r e firit c o a t e d with amorphous, grainy masses, and then rapidly disappeared. The hyd r a t e d tricalciuin afunlinate needin d i c appearc(lmorpslowly, brit iione were found after 7 days. Asmall quantity of gypsum
n~asfound in the 0 8 M solution. HYORLTEDCOXMERCIAL CExmw-The suspension of hydrated cement contained the Same s~bstanct~s found in tho hydrated white cement, but in addition fine crystals of sulfoaluininate were abundant. These may have been
HuifatBlci- On "this su6Figure 2-Ilydrated Commerdal Cement in O A R M MgSO,. Showing pension except that Gypsum Crystals, Amorphous Grain% t h e c o a t i n g on the and a Heaa*onal Cr sfal of Lime PsrtlY Covered wirhGranurarMlateria1. X 100 crvstals of livdrated like was much thicker (Figures 1 and 2). No crystals of hydrated tricalcium aluminate were found after 4 days. G y p snm cryst;tls were rery abundant. Summary White Portland cement made by heating to a high temperature an intimate mixture of powdered marble, alumina, and flint, in tlie proper proport.ions, contained the three compounds, tricalcium aluminate, tricalcium silicate, and 8dicdcium silicate. The reactions of the white cement were different from those of eommeroial cement when both were similarly treated with solutions of sodium and magnesium sulfates. An instance of this diffeimce was the appearance of gypsum in the tests with crystalline commercial cement hut not in the tests with white crystalline cement. Again the reaction products of white cement with sulfates were more like those of the pure cement constituents than were tho produets formed in the case of commercial cement.
INDUSTRIAL A N D E-VGINEERING CHEMISTRY
856
Again the difference in character of the hydrated cements was very apparent, fine sulfoaluminate needles being abundant in the hydrated commercial cement while none were found in the white cement. Lastly, the crystalline grains, as centers of gelatinous particles, lasted for a much longer time in the white cement than they did in the commercial cement. Possibly these differences may be due to the small amount of ground gypsum added to the commercial cement and also to its greater percentage of magnesium and ferric oxides. The presence of silicates seemed to have influenced the speed of disintegration of hydrated tricalcium aluminate crystals, since in the tests with the two varieties of cement
Vol. 18, No. 8
and solutions of sodium sulfate these crystals lasted for a much shorter time than they did in the tests with pure hydrated tricalcium aluminate. Solutions of magnesium sulfate were especially destructive in their action on crystals of hydrated tricalcium aluminate, regardless of the presence or absence of calcium silicate. The character of the layers surrounding crystals of hydrated lime varied with the sulfate solutions used. In sodium sulfate the layers were apparent only on the edges of the lime crystals and were made up of granular masses. In magnesium sulfate solutions the lime crystals were heavily enveloped, the coating frequently consisting of a transparent homogeneous layer as well as granular masses.
The Measurement of Surface Temperatures' I I-Comparison
of Various Methods
By F. W. Adams and R. H. Kean MASSACHUSETTS INSTITUTE OF
A
TECHNOLOGY, SCHOOL
OF
CHEMICAL
LL problems of the flow of heat from solid bodies involve a determination of the temperature of the
ENGINEERING PRACTICE. EASTERN MANUFACTURING C O . , BANGOR, ME.
recently calibrated, millivoltmeter which could be read to closer than 0.5' C. The different methods of measurement tested were in detail as follows:
surface of the solid, and there is a surprising lack of information in the literature on this subject, below the range of optical and radiation pyrometers. Since a large propor(a) T h e compensated thermocouple devised by Boyer and tion of heat-transfer probIems falj in this range, the present Buss at this station, consisting essentially of a thermocouple investigation was conducted to determine the reliability of held against the surface and compensated for heat losses by various methods of surface tempereture measurement and to means of a small electric heating element. ( b ) A thermocouple whose hot junction was imbedded in compare their precision and general applicability. the wall of the steam chest, as recommended by Foote, Fairchild, The investigation included a ktudy of the precision ob- and Harrison.3 The wires were inserted into a small hole drilled tainable in the measurement of surface temperatures by the about 2 mm. into the surface and held in place by a soft copper plug driven in with them. use of a mercury thermom(c) A thermocouple whose eter, of thermocouples with h o t j u n c t i o n was soldered soldered hot junctions, of a onto the surface. The results obtained by various methods of measurthermocouple in which the ( d ) A device made of two ing the temperature of a metal surface between 100' No. 14 B. & S. gage thermometal surface served as a and 150' C. are presented and discussed. A thermocouple wires clamped into a hot junction, and of a thercouple compensated for heat losses was found to be wooden handle leaving about mocouple compensated for 3 mm. of each protruding. the most accurate method. This device has been sucheat lossesl2and was limited These ends were sharpened cessfully applied to the measurement of the temand pressed firmly against to a range of temperatures peratures of a wide variety of metallic and nonmetallic t h e s u r f a c e t o make the c o n v e n i e n t 1y obtainable surfaces, including moving surfaces. c o n t a c t between the wires with steam as a heating t h r o u g h t h e metal of the steam chest itself. medium. Experimental Procedure
The measurements were made upon the surface of an iron steam chest between 100' and 150' C., and the results compared with the temperature of the steam within, and with the calculated surface temperature. The steam chest was equipped with a pressure gage and thermometer well, giving a knowledge of the conditions within, as a basis for the estimation of the precision of the various measurements. The steam temperature could be maintained constant within 0.3O C., and during the tests care was taken to eliminate disturbing air conditions which might distort the readings. The thermocouples used in the investigation were all made of chrome1 and cope1 alloys, and except where otherwise mentioned were of No. 22 B. & S. gage. They were all calibrated before use against an accurate thermometer, which was used for determining the temperature in the steam chest. The e. m. f.'s generated by the thermocouples were measured on a new, Received March 12, 1926. 1 Boyer and Buss, TXISJOURNAL, 18, 728 (1926). 1
(e) A thermocouple whose hot junction was placed under a n asbestos pad held firmly against the surface. (f) A thermometer whose bulb was placed under a n asbestos pad held firmly against the surface.
Results
The results obtained on the surface of the steam chest by the various methods are presented in Table I, and in Figure 1. The temperature of the surface (Curve 2, Figure 1) was calculated from the temperature of the steam4 to be between 0.3' and 0.6' C. below the steam temperature. The temperature indicated by the compensated couple is shown to fall on the same line as the calculated surface temperature (Curve 2). The imbedded couple (Curve 3) falls about 1O C. below this line, while the couple soldered to the metal surface gives a reading about 3" C. low (Curve 4) over the range studied. The other methods give results further away from the true surface temperature (Curves 5, 6, and 7 ) . a 4
Bur. Standards, Technologic P a P n 170, p. 298. Walker, Lewis, and McAdams, "Principles of Chemicat Engineering; '
1923, p . 170.
