of aluminum hydroxide. The Si02 content of the amorphous hydroxide precipitate is higher, the lower the temperature during precipitation. With a high A1203: SiOz ratio in solution the dissolved silica is almost completely precipitated. The pH of the solution has only a slight effect on the A1203:SiOz ratio of the precipitate. When using sea water, the X-ray amorphous precipitates contain other ions, especially mag- nesium; this could be of significance in the diagenesis of clay minerals from these hydroxide-silica precipitates

On attempting to prepare the dihydrate MgS04-2 H20 (sanderite) R . v. Hodenberg and R. Kuhn (Hannover, Ger- many) repeatedly obtained two hydrate phases, of still uncertain composition, whose crystals grew together with the same orientation. For one of the two phases the lattice constants an = 12.35 A, bo = 12.40 A, cg = 13.25 A, p = 91.5 (C2/c) were found. Moreover, the authors prepared an ortho- rhombic trihydrate MgS04.3 H20, not described before, with lattice constants a0 = 8.18 A, bo = 10.93 A, co = 12.42 A (Pbca, pexp. = 2.06 g cm-3).

W. Eysel, M . Behruzi, and T. Hahn (Aachen, Germany) investigated the system LiGaSi04/LiGaGe04/LiAlGeO4/ LiAISi04. While LiAISiO4 has the $-quartz structure at normal pressure, the first three compounds crystallize as the phenakite type and are completely miscible. Cd2Ge04 is isotypic with y-CazSiO4 and y-CazGeO4 (olivine type); how- ever, CdzSi04 crystallizes as the Na2S04 (V)-type. Therefore, at high temperatures only limited mixed-crystal formation between the two cadmium compounds was observed. Cd3SiOs is orthorhombic-pseudotetragonal and structurally related to Ca3SiOs; however, Sr3SiO5, Ba3SiOs and Ba3GeO5, K3BeF5 and Rb3BeFs possess full tetragonal symmetry. Sr3GeO5 and Cd3Ge05 could not be synthesized.

G. H . Moh (Heidelberg, Germany) investigated the binary system tin/sulfur and found that SnzS3 and SnSz exist as stable phases as well as Sn, SnS, and S. The hexagonal layer structure of the disulfide is transformed sluggishly at 692 ‘C into the cubic structure which is stable up to the melting point. Also Sn2S3 has a transition point at 738OC and melts in- congruently at 758 “C. Knowledge of the stability relation- ships finally brought about the discovery of Sn2O3 in Bolivian tin ores. An investigation of cadmium titanate at high pressures (up to SOX lo3 atm) by J. Liebertz (Aachen, Germany) and C. J . M. Rooymans (Eindhoven, Netherlands) lead to the unexpected result that the temperature of transition from the low-tem- perature form a-CdTiO3 (ilmenite type) to the high-tem- perature form F-CdTi03 (perovskite type) decreased with increasing pressure. This implies that cr-CdTiO3 is less dense than the p-form. While the phase transition cr + p in air above 925OC is irreversible and very slow, the reverse reaction can be observed under hydrothermal conditions at 850 OC.

G. Bayer and W. Hoffmunn (Zurich, Switzerland) prepared, by solid state reactions, compounds with the formulae Nax(ByTi8-y)Ol,j where B = Mg, Co, Ni, Zn, AI, Ti(II), Ti(III), Cr(lII), Fe(III), and Ga. The range of phases ex- tended, for the compounds with trivalent B ions, from NazBzTi6016 to Nai.~3B1.33Ti6.6,016, and for those with bivalent B ions from NazBTi7016 to Na1.6B0.8Ti7.2016. All these compounds are isotypic with the titanium bronzes Na,Ti02, described by Wudsley. The Ti and B ions are statistically distributed over the octahedral sites in the crystal lattice, while the Na ions are surrounded by eight oxygen atoms for valence reasons. Substitution for Na by K, Rb, and Ba leads eventually to non-stoichiometric compounds isotypic with priderite. The painstaking investigation of the structure opthe mineral denningite (Mn, Ca, Zn, Mg)TeZOS bq E. M. Wolitzi (Graz, Austria, and Gottingen, Germany) gives information con- cerning the structure of tellurites. In this structure the Te atom forms a trigonal pyramid with three oxygen atoms. Two such Te03 pyramids are joined by a common oxygen

atom into a Te205 group, such that the Te-0 distance within the Te205 group is, o n average, 1.92 A. The coordination of each Te atom is completed by a fourth oxygen atom, at a distance of 2.36 A, belonging to another Te205 group. The coordination of the Te atoms as well as the Te-0-Te bond angle of 120 O indicate considerable covalent character of the Te-0 bond. LizZnC14.2 H20 contains, according to H . Jucohi and B. Brehler (Clausthal-Zellerfeld, Germany), [ZnCl4]2- tetra- hedra, while each L P ion is surrounded by four CI- ions and two HzO molecules. In half of the [LiC14(H20)2]3 octa- hedra the water molecules occupy the cis-positions, and in the other half they occupy the trans-positions.

S. Chose, M. Fehlmann (Zurich, Switzerland) and J. J . Finnej, (Golden, Colorado, U.S.A.) found two types of copper polyhedra in the crystal structure of cornetite, Cu3P04(0H)3. Two thirds of the Cu atoms have tetragonal-pyramidal [4 + I]-coordination, and the others have very distorted tetragonal-bipyramidal [4 + 21-coordination. These poly- hedra are combined by common corners and edges into a three-dimensional network, in which the [PO,] groups are found. Of great interest was a comprehensive paper by W. Gentner (Heidelberg, Germany) o n the determination of the age of planetary materials, in which he showed that, contrary to popular opinion, methods by which the concentration of a gaseous decomposition product is measured (K-Ar methods, U/Th-He methods) offer advantages over those using solid decomposition products, because the isotopic composition of the original lead is unknown, while the original rare gases are practically no longer available on Earth. Measurement of the K-Ar age of a large number of chondrites frequently showed that they had an age of ca. 0 . 5 ~ lo9 or ca. 4x 109 years. Presumably then, these stony meteorites from our planetary system originated from two heavenly bodies which solidified 0 .5~109 and 4x109 years ago. The so-called “ra- diation age”, obtained by examination of the outer crust of the meteorite which has been exposed to cosmic radiation, enables the point of time of disintegration of a heavenly body to be established. For stony and for iron meteorites the “radiation age” is usually 2x 107 to 3x lo7 and 5x 107 years, but the small number of meteorites examined yields little definite information about how many cosmic catastrophies the meteorites which reach Earth have passed through. There has been much controversy as to whether tektites are glasses of volcanic or of meteoric origin. The determination of their “radiation age” gave (14.9 & 1) Y 106 years for tektites from the Nordlinger Ries, and (14.8 + 0 . 6 ) ~ 106 years for the moldavites found in Czechoslavakia, which, together with other findings, indicates a genetic linkage between the two. The isotopic composition of argon contained i n the many blow-holes in the tektites indicates that the material is terrestrial matter which probably melted when striken by a

[VB 859/169 IE] meteor. German version: Angew. Chem. 77, 45 (1965)

Synergic Effects in Solvent Extraction

H. Irving, Leeds (England)

Synergism in the liquid-liquid extraction of inorganic cations, i .e . the phenomenon whereby a mixture of two reagents produces a larger value for the extraction coefficient than either reagent taken alone, was originally believed to occur only with uranium(V1) and certain mixtures of phosphorus- containing extractants. In 1959, Irving predicted that the effect would be much more general and demonstrated the very large synergic effect in the extraction of uranium(V1) by mixtures of TTA (thenoyltrifluoroacetone) and TBP (tri- butylphosphate) or TBPO (tributylphosphine oxide). The effect was later demonstrated with other actinides in various

Angew. Chem. internat. Edit. / Vol. 4 (1965) / No. I 95

oxidation states, with lanthanides, with transition metals of the first series, and even with alkaline earths. In the lecture, examples were given of synergism in the solvent extraction of indium, protactinium, and plutonium by various combinations of reagents and solvents. An account was also given of other unpublished work o n the uses of heterocyclic amines and diamines to promote the extraction of copper(I1) by acetylacetone, cobalt(1l) by TTA, and nickel by diacetylbisbenzoylhydrazone. The compositions of the extractable adducts have been determined in various ways and a reduction of the synergic effect caused by a-

substitution in pyridines can be attributed to steric hindrance of coordination. Where the solvent extraction of the bischelate CoT2 [*] is enhanced by either of two bases A or B due to the formation of the extractable adducts CoTzAz and CoT2B2, an addi- tional synergic effect may arise from a mixed complex CoTzAB, and evidence for such mixed complexes can be

[VB 839/188 IE] obtained in this way.

German version: Angew. Chem. 77, 57 (1965) -

[*I T=Thenoyltrifluoroacetone.

SELECTED ABSTRACTS

An apparatus for maintaining the pH of unbufferd solutions has been constructed by C . W. Cotman and D . M . Smith. A pH- meter with a simple combination of a glass electrode and a reference electrode gives a signal indicating any change in pH through a servo system which, depending on the sign of the pH difference relative to the desired constant value, dis- charges strong acid or strong base (of a concentration depend- ent upon the pH value to be maintained) from one of two syringes. The instrument can maintain any pH value between 2 and 10 constant to better than 50.05 unit for 48 h, provided that the temperature of the unbuffered solution is kept con- stant. / Rev. sci. Instruments 41, 561 (1964) / -Hz.

[Rd 110/297 IE]

Pure difluoroborane HBF2 has been prepared for the first time by T . D . Coyle, J . J . Ritter, and T. C . Farrar. HBFz was al- ready suspected as an intermediate in the reaction of diborane with fluoro-olefins; here it is best obtained from BF3 and di- alkoxyboranes at O°C; the product is frozen out as a mix- ture with BF3 and a little diborane. The products are sepa- rated by vacuum distillation, but this leads to considerable loss of HBF2. The compound disproportionates gradually at room temperature into BF3 and diborane; addition of di- borane slows down the disproportionation. HBF2 reacts smoothly with ethylene at room temperature to give ethyl- boron difluoride. / Proc. chem. SOC. (London) 1964,25 / -Gn.

[Rd 145/332 IE]

Novel complexes of metallocenes with it-acceptors were isolated by J . C . Coan, E. Berg, and H. E. Podall. ( 1 :2)- Nickelocene-p-chloranil ( I ) is formed from its components in benzene in 76% yield as a dark brown solid which is stable in air and up to 35OoC under argon; it is soluble in water and benzene. (1 : I)-Cobaltocene-p-chloranil (2) [92 yield] is olive green and decomposes at 1O5-11O0C; the (1 : 2)-complex (3) [78 % yield] is da1 k green and decomposes at 228 'C. (1 : I)-Cobaltocene-l,3,5-trinitrobenzene (4) [95 %, yield] is brown and stable in air; its m. p. is 125 "C. Ferrocene forms complexes in the melt and in some solvents with p - benzoquinone, tetrachlorophthalic anhydride, 1,2,4,5-tetra- cyanobenzene, etc., but these cannot be isolated.

x-Cp2NiZ@CAz@CA (1)

0 0 x-cpzco '@TNB" + x-CP,CO t- TNB. (4 )

0 0 z-CP~CO CA- CA (3)

Cp = Cyclopentadienyl, CA = p-Chloranil, TNB = 1,3,5-Trinitrobenzol

Complexes of this kind are the intermediates sought for in the preparation of metallocinium salts of aromatic acids by oxidation of metallocenes, e.g. with benzoquinone in the

presence of acid [I] . Infrared and ultraviolet spectra reveal that it is the central metal ion and not a n-cyclopentadienyl ring which functions as x-electron donor. This ion combines with the aromatic radical anion (detected by ESR spectro- scopy) to form either a charge-transfer complex with partial charge separation such as (2) or (4 ) - which can disso- ciate into ions in polar solvents such as methanol - or a charge-transfer radical ion salt such as (3). Because of the weakness of its ESR signal, (I) is formulated as a nickel- ocinium salt in which the primary radical ions have undergone disproportionation. / J. org. Chemistry 29, 975 (1964 / -Bi.

[Rd 156/343 IE]

The structures of macrocyclic condensation products obtained from veratrole and resorcinol with aldehydes were elucidated by H. Erdtman, F. Haglid, and R . Ryhage. Acid-catalysed condensation of veratrole with formaldehyde affords two crystalline compounds. It was confirmed by mass spectro- metric and NMR studies that one of these does in fact possess the structure already assumed by Lindsey [2] with three veratrole rings and a "crown" conformation of the nine-membered ring. The second compound has the structure ( I ) . A crystalline product obtained by condensing resorcinol with acetaldehyde in the presence of sulfuric acid has the

P? R R

HO -OH

structure (2). / Acta chem. scand. 18, 1249 (1964) / -Ma. [Rd 1501337 IE]

Prismatic samples can give wrong transparency values in the infrared, as A. L. Olsen, K . B. LaBaw, and L. W. Nichols have found. The prismatic form of the sample causes the beam of light that has passed through it to enter the monochromator at an oblique angle and therefore disturbs the conditions of the optical beam balance. The magnitude of the error in the transparency is given in terms of the angle of the prismatic layer and index of refraction of the sampIe; the error in- creases with increasing prism angle and with increasing re- fractive index. / J. opt. SOC. American 54, 813 (1964) / -Hz.

[Rd 112/299 IE]

[ I ] Cf. G. Wilkinson et al., J. Amer. chem. SOC. 74 , 2125 (1952). [2J A. S. Lindsey, Chem. and Ind. 1963, 823.

96 Angew. Chem. internat. Edit. 1 Vol. 4 (1965) / No. I