52. Lanthanum Oxalate Decahydrate, La,(C,0,),.10H20 Contributed by VICTOR GILPIN, Michigan State College, Lansing, Mioh., and WALTER C. McCRONE, Armour Research Foundation of Illinoid Institute of Technology, Chicago 16, 111. deeahydrate is too insoluble to recrystalL lize from oxalate water. Excellent crystals, however, can he ohANTHANUM
tained using a procedure adapted from Wylie ( 1 ) . One per cent solutions of oxalic acid and lanthanum nitrate acidified with nitric acid are added dropwise to water maintained a t about 50' C. The addition of 100 ml. of each solution to about 100 ml. of water should require about 2 hours. The resulting crystals should he filtered immediately. Mare dilute solutions yield larger crystals more suitable for single crystal x-ray measurements.
layers parallel to 010. Furthermore, as the witter leaves the lattice most of the shrinkage occurs along the b axis. The net result is a very large increase in density and 8 large increase in the alpha refractive index. This collapse of the lattice during dehydration differentiates this type of structure from the zeolite type, since the latter can he dehydrated reversibly. L m thanum oxalate once dehydrated cannot he rehydrated without complete recrystallieation. The anhydrous oxalate is apparently stable in air indefinitely, but when placed in water on a microscope slide quickly transforms through the solution phase to the decahydrate. ,.eI
*,
#.OB 11/5
B
A
Figure 1. Crystals of Lanthanum Oxalate A. B.
h a h y d r a t e as precipitated Anhydrous crystals after heating for 3 houn at 220' C . ,.a*
Wylie ( 1 ) describes the oxalates of lanthanum,
0
IIYC.
Cerium, and Yttrium as "interstitial" hydrates because of their resemblance t.o the
26.5-b
~
~
\
a0
10
*,*
-
10
-0
I_
Figure 3. Effect of Heat on Three Refractive Indexes, Birefringence, Extinction, Density, and Water Content of Lanthanum Oxalate neat-
zeolites. Lanthanum oxalate preoipitsted as described above molecules a analyzes of- water. to give ~The 10.2
l"g
~
single crystal x-ray data can he used to calculate a molecular weight and the value IO0 010 calculated corresponds exI' actly to that of hydrate containing 10.2 molecules of water. As most of the water Figure 2. Orthographic of crystallization is lost withProjectionof Typical Cryout apparentdamage the tal of Lanthanum Oxacrystal lattice, an attempt late Decahydrate was to determine the x-ray data for the form. The results wore completely negative; large well-formed orystals of the anhydrous oxalate prepared by h e a t ing for 4 hours a t 220° C. gave neither a powder pattern nor a single crystal pattern. The anhydrous oxalate is amorphous in spite of its appearance (Figure 1, B). In an effort to learn more about the dehydration mechanism during heating of the deeahydrate the optical properties, density, and water content were studied as a function of heating time (Figure 3). thzt the study f, these data the of wylie water of hydration is held interstitially; it is not an integral part of the lattice. It also suggests that the water is held in
Time, Temp., Mi". C. 7-e 226 192 94 0.033 0.012 0 20 0.13 42 GO
187
213 218 221
1.615 1.650 1.55
0.005
1.656
1.660
1.661
Or003
1:668
1.67
1:6?1
Extinction. 8AC 26.5 obtuse 14.0 bets 1 2 . 0 \ acute 17.0
...
30.0
+.,
8
e 1.59 1.64 1.47
beta
Density 2.32
.._ ... ... ...
3.30
...
'1
11.652 .625
1.60
water, Moles 10.2
... ... ...
6.1 0.6
In spite of the variable composition of the deeahydrate, the optical pioperties of this phase given below are reproducible and accurate. This is because the phase formed hy precipitation as outlined above is always the decahydrate. The water content of this phase is usually about 10.2 to 10.3 moles. The refractive indexes of six different batches of decahydrate precipitated a t temperatures ranging from 20' to 80' C. were within the limits Of error given below.
cRYSTAL M~~~~~~~~~
Crystal System. Monoclinic. Form and Habit. Rods elongated parallel to c showing the clinopinaooid 10101, ohhopinacoid 1~001,and the clinodome j0111. Axial Ratio. a:b:e = 1.233:1:1.084, Interfacial Angles (Polar). 011 A 011 = 87".
225
226
ANALYTICAL CHEMISTRY
Beta Angle. 119". Twinning Plane. 100. Cleavage. Parallel to 010.
(As might be expected with a structure of this type, the powder diffraction lines are broadened and the intensities are difficult t o estimate.)
X-RAYDIFFRACTION DATA Cell Dimensions. a = 11.91 A.; b = 9.66 A . ; c = 10.47 -\. Formula Weights per Cell. 2. Formula Weight. 722 (decahydrate). Density. 2.30 (flotation and pycnometer); 2.29 (x-ray).
OPTICALPROPERTIES Refractive Indexes (5893 A . ; 25' C.). QI = 1.473 f 0.002; j3 = 1.548 zk 0.002; y = 1.601 =I= 0,002. Optic Axial Angle (5893 A.; 25' '2.). 2V = (-) 77". Optic Axial Plane. I 010, y A c = 63.5' in obtuse beta. Extinction. j3 A c = 26.5" in obtuse beta.
Principal Linea d 10.55 6.76 5.28 5.07 4.86 4.57 4.32 3.79 3.58 3.05 2.96 2.91 2.83 2.78
I/Il
d
1/11
ACKNOWLEDGMENT
0.5 1.0 0.5 0.5 0.7 0.1 0.1 0.2 0.3 0.5 Very weak Very weak 0.2 0.1
2.70 2.63 2.39 2.33 2.29 2.26 2.21 2 11 2 08 2.03 1.99 1.58 1.54
Very weak 0.1 Very weak Very weak Very weak Very weak Very weak Very weak Very weak Very weak Very weak Very weak 0 1
The authors gratefully acknowledge the assistance of the Research Corp. in making this study possible.
A Practical Manual of Rubber Hardness Testing. A . L. Soden. 49 pages. MacLaren & Sons, Ltd., Stafford House, Korfolk St., London, W.C. 2, England, 1951. Price, $1.25.
This manual on rubber hardness testing, which compiles available information on various methods for measuring hardness, is most welcome as a convenient reference n.ork. A manual on this subject has long been overdue. The Shore A2 durometer has not replaced the quadrant Shore instrument in the L-nited States. The A-2 instrument is not as accurate and does not hold ita calibration long enough throughout the hardness range to be of practical value. The Res gage, it should be pointed out, gives a hardness reading without any change due t o creep. A distinct advantage is that the Res gage can be removed from the rubber and read under convenient light. Some observers who are used t o reading hardness on a dial gage have difficulty in reading hardness on a vernier scale. The S.IE-.ISTM Technical Committee on Automotive Rubber has shown that conversion for various scales of hardness when applied to synthetic rubber compounds are inaccurate and unreliable. .In instrument vihich would furnish a positive procedure for measuring indentation pressure is highly desirable and would be a distinct contribution to the problem of hardness testing. H. -4.WIXKELIIAVX
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Quantitative Organic Microanalysis. Al Steyernark. sii 389 pages, The Blakiston Co., 1012 Walnut St., Philadelphia 5 Pa., 1951. Price, $7.00. This small volume contains an admirably condensed treatment of the methods of the organic microanalyst. The procedures are mostly those of Pregl modified in detail to adapt them to present working conditions in an active American industrial laboratory. Constant attention is given t o minutiae of operations which it must be admitted are important in obtaining reproducibility, especially nith average analytical personnel. Details follow implicitly those specified by the Committee for the Standardization of Microchemical hpparatus and the Association of Official Agricultural Chemists, and represent the best standardization now available. Some additional material not ordinarily included in conventional treatises on microcombustion methods is included, notably the Van Slyke manometric methods and some physical property methods. At the end of each chapter is a condensed summary of additional procedures and applications which
LITERATURE CITED
( 1 ) Wylie, A. W.,
J. Chem. Soc., 1947, 1687.
COXTRIBUTIOKB of crystallographic d a t a for this section should be sent t o Waiter C. NcCrone, Analytical Section, Armour RePearch Foundation of Illinois Institute of Technology, Chicago 16, Ill.
intrigues the reader's curiosity without quite satisfying it. This section contributes a large proportion of the references, and probably represents most of that which is of interest t o the research analytical chemist. This volume should be of great value in training of microanalysts, both in universities and industrial laboratories because of its clear and detailed presentation. I t will have less interest as a reference for research workers. PACLL. KIRK Chemische Optik. Hermann Mohler. 296 pages. Verlag H. R. Sauerlander & Co., .larau, Switzerland, 1951. Price, 23 Swiss francs. This book presents a very basic introduction to the theory and application of optical methods t o chemical analysis. The first section synopsizes the physical theories of light, matter, and their interaction in a very elementary manner. Section two mentions those optical measurements utilizing monochromatic light, and the third those depending on spectrally dispersed light. The fourth section concerns itself, again briefly, with the relationship between optical properties and chemical constitution. I n encompassing this a i d e field of chemical analysis as well as attempting a mathematical presentation of the underlying physical-optical theories, the author is of necessity rather brief. The attempt to familiarize the beginning student with the most recent concepts falls short of this goal by several years. References, in general, are to standard European texts, and not to the journal literature, recent or otherwise. The text is primarily a survey and in this regard presents an elementary review of well-known instruments and well-established methods. For anyone unacquainted with the ramifications of optical methods in chemical analysis, the book is interesting reading, although lacking in detail. A h p o n eacquainted with the field 1% ill find a survey of fundamentals, undoubtedly already gleaned elseHWS J. STOLTEN 15-here.
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Optical Crystallography. Ernest E . TTahlstrom. 2nd ed. vii 247 pages. John Wiley & Sons, 440 Fourth Ave., Kew Tork, 16, N. Y., 1951. Price, 84.50.
I n the second paragraph of his preface, the author of this sturdy book has chosen to emphasize the contribution of optical crystallography to chemistry. It is appropriate therefore to mention that his point of view throughout is that of a geologist. The
