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INDUSTRIAL AND ENGINEERING CHEMISTRY
December, 1925
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Action of Sodium and Magnesium Sulfates on Calcium Aluminates’s2 ’
By G . R. Shelton UNI~BRSITY OR SASKATCH~WAN, SASXATOON, CANADA
Preparation
H E c o m p o u n d s 5:3
In the second paper’ concerning the action of “alkali” waters on Portland cement the author discussed the effect of solutions of sodium and magnesium sulfates on the compounds present in Portland cement clinker. The present investigation comprises an extension of those tests to include the calcium aluminates, which are the only other compounds in the ternary system CaO-A120rSi02 having cementing properties on hydration.4~6 Of these the 5:3 calcium aluminate (5Ca0.3A120a) and the monocalcium aluminate (Ca0.A1208) are important constituents of highalumina cements,@ which cements withstand the disintegrating action of sulfate solutions for a much longer time than does Portland cement.
c a l c i u m aluminate (Ca0.and 3 :5 calcium aluminate (3Ca0.5A1203) were prepared in the same manner as the calaium silicates, the heat treatments being so conducted that the resulting clinker in each case was well sintered but not fused. The raw materials were commercia1 alumina and powdered white marble. Al203),
Table I-Analysis of the Aluminates, i n Per cent Loss on Insoluble ignition residue CaO AlzOs 0.10 0.40 47.60 51.01 5CaO.3AlnO~ CaO.Aln0s 0.16 0.58 34.74 64.83 3Ca0.5Al:Os 0.20 0.34 24.82 74.67
MgO 0.36 0.40 0.39
The optical properties of these compounds checked with the data given by Wright.’ Crystalline Aluminates with Sodium and Magnesium Sulfates
Five solutions of each sulfate were employed, having the following molar concentrations, 0.05, 0.1, 0.2, 0.4, and 0.8. Mixtures of 0.08 gram of the aluminates with 5 cc. of the above respective solutions were made in stoppered tubes, as described in the tests on the constituents of Portland cement. Microscopic examinations of these suspensions mere made a t intervals of 1 to 5 days as long as evidences of change were noted. SODIUMSuLFaTE-(a) 5:s Calcium Aluminate (5CaO.5A1203). Hexagonal crystals of hydrated tricalcium aluminate were noted in the 0.05 M solution, but disappeared after 2 days. Fine needles of sulfoaluminate were present in all of the mixtures, the size of the crystals diminishing as the concentration of the sulfate solutions increased. These crystals continued to grow slowly till the suspension in 0.05 and 0.1 M solutions became quite viscous. Small, rounded grains of gel were found in the mixtures, and some larger masses which may have contained unhydrated 5:3 calcium aluminate in the centers. This was quite evident in the 0.8 M solution, owing t o the clear centers in a number of grains. However, the fact that the original aluminate grains were isotropic made them invisible between crossed nicols. Further examination showed very little change after 8 weeks, except
* Received June, 24, 1925. 3 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 Shelton, THISJOURNAL, 17, 589 (1925). 4 Endel, Zcment, 8, 319 (1919). 8 Bates, Bur. Standards, Tech. Pafier 197. Dyckerhoff, Zement, 18, 339 (1924). 7 Am. J . Sci., (41 89, 75 (1915).
for the gradual growth of sulfoaluminate crystals.
(b) Monocalcium Aluminate (CaO.AlzOa). T h e changes were similar to those occurring in the 5:3 calcium aluminate, but occurred more slowly. Hexagonal crystals of hydrated tricalcium aluminate were noted in the 0.05 M solution on the fifth day, but disappeared in a few days. Sulfoaluminate crystals were found in all the solutions. The suspension in the 0.1 M solution became semisolid on the third day (Figure 1). Layers of gel surrounded all the original grains, the latter disappearing in 0.05 and 0.1 M solutions but traces remained in the other solutions after a month. These crystalline cores, being anisotropic, were easily distinguished between crossed nicols. (c) 5:6 Calcium Aluminate (SCaO.6pl203). The reaction proceeded very slowly and the products were the same as in the tests with the other aluminates, with one exception; no hexagonal crystals of hydrated tricalcium aluminate were found in the 0.05 M solution. Small quantities of sulfoaluminate crystals and amorphous grains were formed so that all the suspensions remained quite fluid. Large quantities of original grains covered with layers of gel were found in all the tubes after 10 weeks. MAGNESIUMSULFATE-(a) 6:5 Calcium Aluminate (5 CaO.SA1203). Layers of gel appeared around all the original grains in 18 hours. These grains disappeared in the 0.1 M solution after 3 days. Sulfoaluminate crystals were found in the 0.05 M solution and also hexagonal plates of hydrated tricalcium aluminate crystals. The latter crystals remained in this solution for 2 months. Gypsum crystals were noted in all the other solutions. Rounded fragments of clear gel were abundant in all the solutions and remained unchanged. ( b ) Monocalcium Aluminate (CaO.AZ203). Reaction products were the same as with the 5:3 aluminate, but the changes took place more slowly. Gel surrounded the original grains in the 0.05 M solution on the second day and were noted on the grains in the remaining solutions on the fifth day. Traces of crystalline cores in the amorphous particles in the 0.05 M solution were noted after 4 weeks. These cores were more abundant in the more concentrated solutions. Sulfoaluminate crystals were found in the 0.05 M solution and gypsum crystals in the others. (c) 5:6 Calcium Aluminate (SC~0.6A1~03). The reaction products were the same as in tests with the other aluminates, but the changes took place very slowly. After 3 months the original crystals covered with gel remained in all the solutions, being less abundant in the dilute. (Figures 2 and 3) Hydrated Aluminates and Solutions of Sodium and Magnesium Sulfates
Two and a half grams of crystalline aluminate were shaken with 30 cc. of water in a stoppered tube until a microscopic
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INDUSTRIAL AND ENGINEEMS.0 CHEMISTRY
Vol. 17,No. 12
Flgure 6-Hydrated 5:3 Calcium Aluminate In 0.05 M Mnenesium Sulfate Sbowine Cnaree C r ~ s f s of i ~ Sulfoslumlnate In Civsrers and Fins Grained Aluminium Hydroaide. X 100
Figure 7-Idcntlcal w i t h Figure 6 but between Crnased Nlcola Showing Extremely Small Crysfsla of Hydrated Trlcalclum Alumlnafe and Needles of Suifoalurninate. x ino
Figure 8-Hydrated 5:3 Calcium Alumlnate In 0.2 M Magnesium Sulfate Showlng G ~ o u p e of Small Gypsum Prlsms and Fine Grains of Gel. X 108
F i g u r e 9-Hydrated Monocalcium Aluminate in 0.2 M Sodivm Sulfate Showing Sulfoalumlnare Needles and Amor hous Grains and Long CTYBCBIS or SolPoaiumlnate. x zoo
December, 1925
INDUSTIZIAL A N D ENGINEERING CHEMISTRY
examination showed complete hydration or only a trace of the original crysBalline aluminate left. Mixtures were made usiug 1 cc. of tlie respective suspensions of hydrated ah-' tninates with 5 cc. of sulfate solutions. Soniuv SULPATE-(~) 5:.3 Culcium Aluminate (,5CaO.3AZzOs). In the hydrated suspension only crystals of hydrated tricalcium aluminate and small fragmends of amorphous matter were present. Sulfoaluminate needles were formed 24 hours after mixiug with the sulfate solutions. Radiating groups of these needles appeared in the 0.05and 0.1 M solutions, becoming $0 abuiidant in the latter that the resulting suspension was quite viscous. (Figure 4) In 20 days it was almost solid. Iiexagonal crystals of hydrated trioalciurn aluminate were noted in a11 the solut.ionsafter 5 weeks, traces being found in the 0.8 :lf solution. Bmorphous grains gradually diminished in size, disappearing in all the solutions except for traces in 0.8M . (Figure 5 ) ( b ) Monocalcium AZuminute (CUO.AZ* Oa). The amorphous m a t t e r was m o r e abundant in this hydrated s u a pension than in that 01 5:3 calcium a l u m i n a t e . Hydrated tricalcirtrn aluminate crystals in a h u rid a n c e were noted. Reaction products with sulfate s o l u t i o n s were the same as in tests witti the 5:3 compound. The suspension in 0.1 M became too viscous F l ~ v r e IO~--ldencicnl wirh Fisure 9 but between Crossed N l c d s Showing to flow on the fourth Very Smdl Needles of Hydrated Trialday. Eexagonal cium Aiurninefe. X 100 .. . . triCalcium a s U r n l i l ~ t e crystals disappeared rapidly, none being found ill 0.8 &f solution after 4 days and only traces in 0.05.V after a week. ( e ) ?:.5 CuZ~iumAZumi?mlc (SCa0.iiAZ203). The ciystalline material was very slow in hydrating, but the same products were found as with the other aluminates, with a larger quantity of amorphous matter. Reaction products with the sulfate so1ui.ions were identical wit.h those in the other aluminates, hut the proportion of :tmorplious matter to sulfoaluminate crystals was greater. The suspensions in 0.05 and 0.1 111 hecame x r y om, but flowed in the tubes. Hexagonal tricaloium alumitlate crystals disappeared in 2 days in all except the 0.05 and (1.1 M solut.ions find in i,hem also after 2 weeks. Hydrated 5 3 Cukium A ZILMAGNNSIUJI SULW.%TE--(~) mimtc (;>CaO.3AZdIJ. Crystals of hydrated tricalcium aluminate rapidly disappeared, none being found after 2 days in any of the mixtures except the 0.05 M , and only in sma.11 quantities in it. Erie crystals of sulfoaluminate appeared in Lhe 0.1 M solution after 4 hours, and in the 0.05 M after 2 days. (Figures 6 aild 7) These suspensions became viscous after 3 weeks. Gypsum was noted in the rcinaining solutions. (Figure 8) Amorphous grains were not affected for a few days, but after 4 weeks they became very small. Tiny fragments of magnesium hydroxide were very abundant. (b) Monocalcium AEuminufe (Ca0..4l,O,). Products were thesameas with the 5:3 aluminate, except that sulfoalominate crystals were noted in tlie 0.05M only and gypsum in the rest.. (Figures 9 and 10) With the exception of a trace of hydrated
1269
tricalcium aluminate crystals in 0.05 &I, none were present in any of the solutions after the first day. Original amorphous grains were very abundant. and remained unchanged. $11 the mixtures were fluid, (c) 3:5 Clclcium AZurniuate (SCa0.5AZ2Oa). The changes were identical with those in the case of monocalcium aluminate, except that very little sulfoaluminate crystals were found and the resulting suspensions were more fluid. There wns no change in the 0.05 A4 solution till the third day, when a trace of sulfoaluminate was noted. The crystals of gypsum grew very slowly in all the mixtures, the largest lieitig found in the most concentrated solutions of magnesium sulfate. KOfurther changes could be noted after 2 weeks. Sulfoaluminate crystals were usually present as fine needles, but sometimes as coarse prisms, and frequently these had short needles growing parallel to each otlier from opposite ends of a prism. (Figure 11) The optical properties were determined oil the coarse prisms, after separating them from t,lie solution and washing with a small quaiitity of water and leaving them in the desicoat.or till just dry, usually less than ati hour. The crystals were optically positive, though the iiiterference figure was indistinct, showing only hazy liars. Axial angle was large and t,he character of the principal zone was negative. Its chief indices of refraction were CL = 1,461 * 0.003 and y = 1.463 * 0.003. These data check with those given by Bates. Summary
I-TIie hydration proditct,aof the three calcium aliuriiriates, 5CaO.3~\l2O1, CaO.BI2Os,and 3CaO.5.llrO3, are hydrated tricalcium aluminate and aniorphous matter differing from that of 3CaO..4l2O:i, which is hydrated tricalcium aliiniinate only. The amount of gel increases with the increase in proportion of alumina in the compoiiiid. The time required for conrplete hydration increases with the alumina content of the compound. 2-The formation of sirlfoaliiirririate crystals is characteristic of the reactions hetween calcium alumiiiatt.s, < axid hydrated, and solutions of sodium sulfate iii :ill conceiitratiCjns, also of magnesium sulfate in conmmations helow ~.(1.1 $1. *4hove this coilr:cntmtion of tlie latter snlt the only cryst,alline product is gypsum. Very large q u a n t i t i e s of sulfoalurninatc crystals arc formed from the hydrated aluminates and dilute sulfate solutions: amorphous grains in the original hydrated suspension being largely used upin the process. 3-Layers of gel surroimd the crystelline aluniiuate grains, protecting thein from further su1fat.e action. and are more plentiful in solutions of magnesium sulfate, prohably being coruposed in wart of amorphous . . m&nesiiim hidroxide. The protection to the cryst,alliiiegrains afforded by the gelatinous layers is most effective in the most concentrated solutions of both sodium and magnesium sulfate, and also with the aluminate having t.he highest alumina content.
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INDUSTRIAL AND ENGINEERING CHEiMISTRY
4-With the crystalline aluminates and the most dilute .sulfate solutions hydrated tricalcium aluminate crystals either did not form or disameared soon after being woduced. This is very different from- the behavior of cry&line tricalcium aluminate in such solutions. I n the latter case the hydrated crystals grow to a large size and remain unchanged for several months.
Vol. 17, No. 12
&The maximum and minimum indices of refraction of sulfoaluminate crystals are respectively y = 1.463 * 0.003 and a = 1.461 * 0.003. Acknowledgment
The author expresses thanks to T. Thorvaldson for helpful suggestions during the progress of this work.
Future Research in the Field of Organic Arsenicals'.' B y Walter G . C h r i s t i a n s e n HARVARD MEDICAL SCHOOL, BOSTON, MASS.
T
HE program adopted by the National Research Council Subcommittee on Organic Arsenicals includes the compilation and publication of a set of problems on which attention should be concentrated. This seems to be a means by which a group of chemists might be induced to attack several allied problems, the results of which would add materially to our knowledge of organic arsenicals. I n undertaking this phase of our work, an appeal was made to chemists and pharmacologists who have been engaged in studies in this field for suggestions regarding worth while problems. The cooperation given is hereby gratefully acknowledged. The problems enumerated in Section A, and Section D-5, are all very closely allied and should be undertaken by people who will cooperate with each other. It would be well, therefore, for those desiring to study these particular problems to communicate with the writer in order that the various phases of the research may be properly correlated. A-Relation
between C o n s t i t u t i o n a n d Properties of Arsenicals
The feeling seems to be quite general, among the chemists who have been consulted, that the rapid production of new compounds should be arrested temporarily, in order that a more complete understanding of the arsenicals which we have at present may be obtained. The writer heartily agrees with this sentiment and has hoped for some time to have an opportunity to study the relations existing between the eighty-odd different derivatives of benzenearsonic acid which he has had occasion to use at various times during his studies of arseno compounds. Although such a possibility seems quite remote, there are probably others who will be able to study these problems dealing with the relations existing between the constitution of the arsenicals and the properties to which biological activity is connected. The results of such a study will make it possible to carry on the future synthetic experiments on a much sounder basis. (1) The relation between the constitution of aromatic arsonic acids and the ease with which they may be reduced to arsenious oxides. The present conception of the behavior of the arsonic acids in vivo stipulates t h a t they are reduced to arsenious oxides. Consequently, a study of the reduction of a large number of such acids and a comparison of the results with those obtained in toxicological and parasiticidal studies of the same acids might enable one t o correlate t o some extent constitution and biological behavior. (2) A complete study of the solubility relations of the same series of arsonic acids as is used in t h e investigation of the reduction of the arsonic acid group. This should include not only aqueous media a t various pH's, but aqueous solutions of various Received October 16,1925. Report of Subcommittee on Arsenicals, Committee on Chemical Research on Medicinal Substances, Division of Chemistry and Chemical Technology, National Research Council. 1 2
salts and organic solvents and the partition of the arsenicals between aqueous and organic solvents. (3) The dialysis of these arsonic acids. This should include the rate of dialysis and the use of various types of membranes. (4) The behavior of these arsonic acids toward various body fluids and nerves, particularly the optic nerve. ( 5 ) Inasmuch as the arylarsenious oxides are considered t o be the biologically active arsenicals, studies analogous t o 2, 3, and 4 should be made, using the oxides corresponding t o the acids used in the preceding studies. (6) The behavior of these oxides toward various sulphydril _ _ compounds, particularly glutathione. (7) The relation between t h e constitution of the arseno compounds corresponding t o the arsonic acids and arsenious oxides referred t o above and the ease with which they may be oxidized t o arsenious oxides. (8) An exhaustive investigation of the physical-chemical properties of these arseno compounds. Comparatively little is known about this phase of arsenical chemistry. The arseno compounds are mainly colloidal substances, the properties of which may be varied between wide limits. Although investigations in this field may be quite difficult, the results should be extremely valuable. (9) The relation between the constitution of the arsonic acids, arsenious oxides, and arseno compounds and the fission of the carbon-arsonic bond. B-Production
of New Organic Arsenicals
.
Inasmuch as organic arsenicals are useful solely as therapeutic agents, the role which they play in chemical warfare will be disregarded for the present, the researches in which new series of compounds are studied are instigated by the desire to obtain substances of greater value than those already known. Some chemists, well versed in the chemistry and therapeutic properties of arsenicals, are quite pessimistic regarding the success of attempts to synthesize arsenicals which can assume important positions in the treatment of parisiticidal infections. While it is indisputable that for any new arsenical which is of sufficient value to be used as a chemotherapeutic agent there must be many failures, the cause is not altogether hopeless; it is only a few years ago that tryparsamide was prepared by Jacobs and Heidelberger . Although there are divers opinions as to the efficacy of this substance, it is being used and many syphilologists are quite enthusiastic about it. It has also been suggested that some time a compound free from arsenic, antimony, or other metals will be prepared which will have marked spirochaeticidal activity. The belief that this will eventually come about is based on the marked trypanocidal activity of the nonmetallo-organic compound Bayer 208. Such a development will be a splendid advance, because there is always a certain element of danger in arsenic therapy. Xevertheless, arsenic research should be fostered. Even though the discovery of valuable medicinals becomes increasingly rare, each of the studies increases our knowledge of this branch of chemistry, and the results, in addition to
