May, 1927
INDUSTRIAL A N D ENGINEERING CHEMISTRY
perimental costs. Many helpful suggestions were made by their representatil-es, and other interested engineers and chemists. Bibliography 1-Daniels, Trade Wastes from Tomato Canning, Report of New Jersey State Board of Health, 1910, p. 248. 2-Stream Pollution by Cannery Wastes, Report of the New York State Board of Health, 1911, p. 825. 3-Baker, Canning A p e , 6, 895 (1925). 4-University of Illinois, Bull. 38, May 18, 1924, Water Surpey Series N o . 11, p. 330.
5-Hommon,
583
U. S. Pub. Health Service, Bull. 118 (September, 1921).
zf
~I~~~~no,",n,".&u~c$~'; ~ ~ 1 . ~ ~ ~ ; , * ~ ; ;fi4 ~ , (1921), 8-Buswel1, Greenfield, and Shive, Ind. Eng. Chem., 18, 1083 (1926). 9-Bishop and Mickle, "Treatment of Wastes from Pea Canneries," Thesis. University of Wisconsin, 1926. 1WAmerican Public Health Assoc., Standard Methods of Water Analysie, 1925. 11-Anon, Canning Age, 4, 13 (August, 1923). 12--Anon, Public Works, 62, 191 (1922). l3-"Stream Pollution in Wisconsin," Joint Report Wisconsin State Board of Health and State Conservation Commission, April, 1927.
An X-Ray Study of Limes Having Different Plasticities' By Marie Farnsworth2 KOSMETALLIC MINERALS EXPERIMENT STATION,BUREAU OF M I N E S , N E W BRUNSWICK, X. J.
Marble and precipitated calcium carbonate are burned in air at 1800", 2000", and 2200" F. and marble in a vacu u m furnace at temperatures from 1200' to 2400' F. in steps of 200" F. The plasticities of the hydrates of all these samples are measured ar,d x-ray powder photographs of the oxides and hydrates taken. The samples burned in a vacuum are found to be more plastic than the samples burned in air. The CaO samples which give a plastic hydr!te give a face-centered cubic pattern with. unit edge 4.79 A; the plastic hydrates give a hexagonal pattern with an axial ratio 1.40. The patterns of the less plastic samples are complicated by additional lines corresponding, if CaO films, to strong lines of the Ca(OH)2and CaC03 films, and if Ca(OH)*films, to strong lines on the CaC03film. In every case the intensity of these extra lines can be taken as a direct measure of the plasticity of the sample; these lines are the same for samples burned at high and low temperatures, but for samples burned at the higher temperatures, the intensity is less. Experiments were not carried out with over-burned samples. Whether or not the Ca(OH)*and CaC03 are the cause of the decrease in plasticity of the lime, or simply an accompanying phenomenon. is discussed.
LTHOUGII lime-burning is one of the oldest known industries, there is very little scientific information in regard t#oit, especially in regard to plasticity. Some limestones will make a good finishing hydrate and other limestones with almost the same chemical composition will not; two limestones of very different chemical composition will often give equally good hydrates. Since the underlying cause does not seem to be chemical, it is natural to seek a physical explanation of this difference, and therefore an x-ray study of the basic materials involved and of hydrates of different plasticities mas undertaken.
A
1) in the Research Laboratory of Applied Chemistry of the Massachusetts Institute of Technology. The tube employed was the usual Coolidge water-cooled molybdenum anode type operated a t 15 milliamperes and 30,000 volts R. ill. S. The x-rays were restricted by means of two slits, 0.5 mm. wide and 10 cm. apart, in a copper cylinder with a lead end. A zirconium oxide filter, free from hafnium, mas placed over the slit near the target. This practically eliminated from the primary beam the white (general) radiation, and the characteristic molybdenum beta and gamma rays. The diffraction pattern, as recorded on the photographic film, v a s therefore caused by the molybdenum alpha doublet. The cassettes ser\-ed as holders not only for the films but also for the specimens. The powdered specimens (finer than 200 mesh) were packed into thin-walled special tubes of glass, free from heavy metals, of about 1 nim. inside diameter and sealed with collodion so that the specimen would not be affected by air or moisture. A septum divided the cassette so that two substances could be recorded directly on the same film. The film ( 1 7 / 8 X 16 inches or 4.7 X 41 cm.) was automatically held on a semicircle of 13 cm. radius a t whose center the specimen was fixed. The use of a semicircle, rather than a quadrant, for powder work permits measurement of the pattern without reference to the trace of the zero beam. The zero beam passed through the sample and on a brass stoppiece, enclosed by a sheet brass baffle to prevent secondary radiation from reaching the film. Sheet aluminum (0.3 111111. thick) was used on the sample side of the film to filter out light rays and to pass the x-rays. .I calcium tungstate intensifying screen was used on the side of the film farthest from the x-ray beam t o cut down the time of exposure. In this manner the diffraction pattern is recorded as a series of lines on the film; the interpretation of various patterns will be given in a later paragraph. Preliminary Experiments
X-Ray Methods
Owing to the nature of the materials to be studied, the pictures were limited to powder photographs as developed by Debye Scherrer3 and independently by Hull.4 The pictures were taken on a multiple diffraction apparatus (Figure 1 Received Kovember 17, 1926. Presented under the title "X-Ray Studies of Limes". Published by permission of the director, IJ. S. Bureau of Mines. 2 Present address, Washington Square College, N e w York University, New York, h7.T. a Kgl. Gesell. R-iss., Gattingen, December, 1915; P h y s i k . Z., 17, 277 (1916). 1 Phys. Rev., 10, 661 (1917).
Preliminary experiments were carried out using ordinary commercial samples. The samples were contained in small glass tubes; a plug of cotton was put in the middle and a sample of low plasticity was put in one end and a sample of high plasticity in the other end. If two oxides or two hydrates were employed, in all cases extra Iines not occurring for the sample of high plasticity appeared on the film of the sample of low plasticity. If two carbonates were used (provided they had approximately the same chemical composition) no difference in lines was observed. These photographs were Yery complicated, as there were lines due to magnesium 6
Clark, Brugmann, and Aborn, J Oblical SOL.Im , l a , 379 (1926).
I,l*DC'STRIdL d S D E S G I X E E R I S G CHEMISTRY
584
aiid calciuiii as re11 as tu tlie inqxirities. so that it seemed almost iinpossible to analyze them completely. Therefore it was decided first to restrict the study to simpler substances, and for this reason only a very pure sample of white marble and Baker's anal-zed C. P. precipitated calciuiii cartionate n-ere einployed. Calcination of S a m p l e s
It has recently heeii foiiiitl liy Haslaiii and Hermannr that the time anti tcniprraturr of h r n i n g liar a great iiiflueiice on tlic resultiiig Iiropcrtie,. of h i e . and t h t from the saiiie saniplc of limehtoiic either R plastic* OT iion-plastic* 1iydr:ctc n--oiiltlrewit accordiilg to the teinperatwe aiitl leiigtli of time of Iiiirning. T1ic.r oli-cr\-ntioiib wcw f o u i i d t o lie true for
1-01. 19, s o . 5
liner clue to carhon appear on the films. After cooling it \\-as removed and ground to pass through a 10-mesh screen and then put into tightly covered tin cans to Irevent airslaking. -1111 runs were made in the same iiianner. H y d r a t i o n of Samples
1Twiglied amomit of the lime n-as placed ill a tin can set into :t h : i h of ruiining cold n-ater. Eiiougli n-ater vas inea>urecl out to hydrate the lime: with 30 per cent exc,ess to take care of cnliorntion. The n-ater i v a ~acitletl s1ou;Iy and T-igorously stirred to prevent the foriiiatiun of lump$ : i d l o c a l over-heating. Thi; iiiethd procluced a dry Iiydratc. D e t e r m i n a t i o n of Plasticity
The pln.ticity of tlie various sarnplei was tehted accordirig to the .>txiitlarcl iiiethod of the -1niericaii Society for Testing IIateriak. Three hundred grimis of lime n-ere hydrated and d t e r aging for one clay were formed into a putty by adding a ufficient quantity of w t e r . This putty was allowed to soak for iiot inore than 81 or less than 16 hours. It n-as then iiiolcled in a r u l h e r ring such as is used with a SXcat needle, resting tlie ~pecimenon a glass plate. The needle used mas a niodifietl form of \ k a t needle! 12.5 min. in diameter and wigliiiig 30 grams, made from aluminum tubing. The lower ciitl w:is closed without shoulder or curvature, and the tube loatled with .hot t o the specified weight. I t was mounted in a \ k t needlc stand. The initial reading was taken with the bottoni c d tlic needle in contact with the surface of the sample; the filial reading. 30 seconds after the plunger was released. A 1Jeiietrntioiiof 20 inin. with a permissible variation of 5 mm. c ) n either side v a s considered standard. If the penetration was less than standard, the sample was renioved from the mold, mixed with niore water, aiid retested; if more than standard, the sample was discarded and a new one prepared. The sample T\-M then ready t o test for plasticity. This was conclucted oil an improved form of the Eniley plasticimeter, the constants of Tyliich were as follows: Xhsorption of base plate: 20 to 25 per cent Dimensions of base plate: 1 inch thick by 4 inches in diameter Dimensions of disk: inch thick by 3 inches in diameter Speed of vertical shaft: one revolution in 6 minutes, 40 seconds Upward movement of base plate: I/I? inch per revolution Torque on disk when bob reading is 100: 14,400 g. c. rn.
Figure 1-Multiple
X-Ray Spectograph
marble and precipitated calcium carbonate. The hainples were burlied in an electric furnace which could be held constant within about 10" F. After the desired temperature was reached and the furnace had had time to heat evenly, 3 to 3 kg. of the prepared limestone were dumped into the clay-graphite, porcelain-lined crucible. This cooled down the furnace, and a inaximum time of 30 minutes was required to bring the furnace and its contents back to the desired temperature. The sample was heated in the furnace for 3 hours before the power was shut off and it was allowed to cool to room temperature. The size of stone employed was 2 to 3 cm In order that the burning of the finely divided calcium carbonate would be as nearly analogous to the marble as possible, it was made into lumps of approximately the same size by means of dextrin. During the burniiig the dextrin was burned out but the lumps still stuck together. At the lower temperatures there was some evidence of free carbon. but in no case did 5
THISJ O I J R ~ A I 18, 960 (1YLbr
The rubber ring previously mentioned was lubricated with a thin film of water placed on a porcelain base plate filled with the paste and struck off level. The mold was removed by raising it vertically without distorting the paste. The base plate aiid paste were placed in the instrument and the carriage was turned up by hand until the surface of the paste was in contact with the disk and the distance between the disk and the top of the base plate was 11/1 inches. The carriage was then thrown into gear and the motor started exactly 120 seconds after t,he first portion of the paste had been put into the mold. The time when the first portion of the paste was put into the mold was recorded as zero time. The scale reading was recorded every minute until the test was complet8ed, The test was considered complete when ( a ) the scale reading reached 100, ( b ) any reading was less than the one before, (c) the scale reading remained const'axit for three consecutive readings ( 2 minutes) and the specimen had visibly ruptured or broken loose from the base plate. The time and scale reading at the end of the experiment were noted. The plasticity figure was calculated from the formula P = Z / F ' + (10 T j ? in which P is the plasticity figure, F is the scale reading a t the '
eiid of the experimeiit, and T i s the time iu miimtes froiii t.lie instant t.he first portion of the paste was put into tho inold l o the end of the test. After each test the porcelttiii base plate i m s wushed with hot water, treated with dilute hydrochloric acid to remove any lime from t.he surface pores, washed agaiii to remow the acid, dried by heating to ahout 100' C., and cooled to room temperature before i t was used again. r. I he results are shown in Table I. Table I-Plasticity
Testa
.. .
~
S,,MPLS
rEMImTURB i)B nuaniai;
i'
YLASIYCIIY
=,
/F
