Basic Acetate Research Articles

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WE have carried out differential thermal analyses of beryllium oxyacetate in order to find accurate transition and melting points and also to examine the heat effect associated with these (Fig. 1). The observed transition and melting points are 148º C. and 286.7º C., respectively. If the sample is heated up to about 250º C. and then cooled to the room temperature, there is observed no transition phenomena in the cooling curve; this behaviour persists, for no transition phenomena is shown by the heating curve obtained on the next day (see curve II). But, when the sample is not heated beyond about 210º C., the transition in the heating curve made on the next day is always observed. The velocity of transition is accelerated by grinding the supercooled sample in an agate mortar. But this effect is somewhat complex. Details of the observation will be reported elsewhere. Comparison of the two peaks in the curves of the thermal analysis reveals that the heat of transition is nearly equal to the heat of fusion.

Polymorphism of Beryllium Oxyacetate

WE have found a transition of beryllium oxyacetate hitherto unrecorded. The transition occurs at about 160º C., and when the temperature is raised above this point the substance assumesgradually the appearance of soft wax, though it melts snarly at 285º C. The melting point of this sub-stance is abnormally high as compared with those of other members of the homologous series, as is seen in rthe figure. It suggests that the high-temperature phase has some unusual structure in which the molecules are held together, forming a crystal lattice, but presumably with a higher order of freedom in its molecular motion, thus resembling the melt in its molecular state. This view is supported by the fact that the intensities of X-ray spectra taken with this phase fall off rapidly with increase of diffraction angles.

On the Color Reaction Between Iodine and the Basic Acetates of Some Rare Earth Elements

Abstract (1) The color reaction between iodine and basic acetate is not, as is often believed, peculiar to lanthanum. It is shown also by praseodymium, neodymium and samarium. (2) The absorption maximum of iodine-basic acetate shifts to shorter wave-length side with the decrease of the basicity of the rare earth elements. (3) The color change of iodine-basic acetate with the lapse of time was studied photometrically. (4) It was confirmed that the sorption isotherm holds good in the cases of the basic acetates of lanthanum, praseodymium and neodymium. (5) The effect of other ions on the color reaction was discussed.

Change of Symmetry of Basic Beryllium Acetate

Preston and Trotter1 have described a change of symmetry with temperature in the Laue photographs of basic beryllium acetate, Be4O(CH3COO)6. This change of symmetry, according to Preston and Trotter, is a reversible one and occurs between 30° and 50° C. At the higher temperature the crystal class possesses three-fold axes with parallel mirror-planes, whereas at the lower temperature only the three-fold axes are present. Preston and Trotter suggest that the increase in symmetry is due to the setting in of molecular vibration of the acetate groups.

A Change of Symmetry with Temperature

DURING the course of an investigation into the effect of temperature on X-ray reflexion in crystals, some photographs were taken of basic beryllium acetate to see whether any of the diffuse reflexions observed by Charlesby, Finch and Wilman1 with electron diffraction in organic crystals could be detected with X-rays. The photographs did not show with certainty any effect of the type looked for, but another effect was observed. At the time (1939), we did not think the matter of very great importance, but recently the results were shown here to Prof. W. T. Astbury, who suggested that they were of sufficient interest to deserve recording.

209. The dipole moments of benzoquinone, beryllium acetylacetonate, basic beryllium acetate, and o-nitrophenol

209. The dipole moments of benzoquinone, beryllium acetylacetonate, basic beryllium acetate, and o-nitrophenol

The Structure of the Carboxyl Group

The crystal structure of basic beryllium acetate, Be4O(CH3COO)6, has been studied by Bragg and Morgan (1), who reported some spectrometric intensity measurements and showed the cubic unit of structure to have ao = 15.72 A and to contain eight molecules, and by Morgan and Astbury (2), who showed the space group to be T4h. In neither study was the atomic arrangement determined. We have found an atomic arrangement which accounts satisfactorily for the data of these authors and for additional intensity data obtained photographically, and which provides information regarding the structure of the acetate group.

Polarisation measurements on basic beryllium acetate and beryllium acetylacetonate

An investigation of organic beryllium compounds is being carried out by one of us (W. R. A.) with a view to obtaining information regarding their molecular configuration and a study of their molecular polarisations suggested itself as a means of deciding whether or not these compounds are spatially symmetrical. No previous attempts appear to have been made to measure the dipole moment of compounds of this type; other physical measurements have been made and will be discussed in a later section. In the present investiga­tion measurements have been made in benzene and carbon tetrachloride solution, but in both solvents the compounds are only sparingly soluble. 2. Purification of Materials . Beryllium Compounds .—Small quantities of basic beryllium acetate and beryllium acetylacetonate were very kindly supplied by Professor G. T. Morgan, F. R. S., and Dr. S. Sugden, and our best thanks are due to them. The melting points of the compounds were in accord with the values quoted at the literature: acetate, m.p. 285° C.; acetylacetonate, m.p. 108-5° C. Micro-chemical analyses, carried out by Dr. Schoeller, in Berlin, gave the following table.

IMPROVEMENTS IN THE ANALYSIS OF MAPLE PRODUCTS

Collaborative work on maple syrup has shown that, with refractometric control, samples can be prepared to a content of 65% solids with much greater precision than is attainable when boiling temperature alone is depended upon. As the dry basic lead acetates used in different laboratories vary greatly in solubility and alkalinity, much better concordance in Canadian lead values can be attained by use of a reagent prepared from normal lead acetate and litharge "activated" at 650–670 °C. The electrical conductivity of solutions containing 25% of solids is less variable in genuine goods than any of the chemical values. The soluble ash is less variable than the insoluble.

The diamagnetic susceptibilities of some beryllium compounds

The investigation of the molecular structure of organic beryllium compounds is being studied by one of us (W. R. A.) from the standpoint of their infra-red absorption spectra. During a mechanical defect in the infra-red apparatus the diamagnetic susceptibilities of basic beryllium acetate, propionate, and pivalate, and of beryllium acetylacetonate were measured in order to obtain further physical data on the structure of these molecules. The susceptibilities were measured on a Curie-Chéneveau magnetic torsion balance by the method previously described by Farquharson. Measurements were made at 18° C. The compounds were finely powdered in an agate mortar and packed tightly into a small graduated glass tube of very slight susceptibility. Packing of solids is most important in diamagnetic susceptibility measurements. In­ efficient packing leads to values of the specific susceptibility much lower than the true value. This diminution results from the fact that the volume of solid is virtually diminished by air spaces and a volume correction should be applied.

Crystal structure and chemical constitution of basic beryllium acetate and its homologues

The physical and chemical properties of basic beryllium acetate, OBe 4 (CH 3 .CO 2 ) 6 , are those of a non-ionised substance having the unitary structure of a typical organic compound, each chemical molecule of which may be regarded as forming one co-ordination complex. The fact that the arrangement of the eleven associating units of which this molecule is composed possesses the geometrical attributes of a tetrahedron has led to a stereochemical conception of the constitution of the compound, which is confirmed by the results of X-ray analysis.

Crystal structure and chemical constitution of basic beryllium acetate and propionate

The co-ordination theory of molecular structure postulates the existence for each valent chemical element of an integer representing the maximum number of associating units which can be grouped around the atomic sphere of the element. This so-called “ co-ordination number ” varies with the atomic volume of the element, and although in the case of elements of medium atomic volume the number is generally six, yet with elements of small atomic volume this number is diminished to four or even less. This conception of co-ordination was elaborated by Alfred Werner into a comprehensive theory of chemical combination and molecular structure long before the electronic constitution of chemical atoms had been revealed, but nevertheless the co-ordination theory has been shown to accord with many of the new facts since discovered by infra-atomic investigations and by X-ray analysis.

The Structure of Basic Beryllium Acetate

THE remarkable compound Be4O(C2H3O2)6, the crystal structure of which Sir William Bragg describes in his letter in NATURE of April 21, p. 532, can be given a chemical formula in complete accordance with its properties. Tanatar and Kurowski have described (Journ. Russ. Phys.—Chem. Ges. 39, 936, 1630; 40, 787; Chem. Centr. 1908, I. 102, 1523; II. 1409) a series of compounds (including the formate, acetate, propionate, and benzoate) of the general formula Be4OA6. These compounds have none of the characteristics of salts. They are volatile, they have low melting-points (some are liquid), they are soluble in organic solvents such as benzene, and they do not conduct electricity.

Crystal Structure of Basic Beryllium Acetate

PROF. G. T. MORGAN recently sent me some well - formed crystals of basic beryllium acetate Be4O(C2H3O2)6, suggesting that their analysis by X-ray methods would, in all probability, be of considerable interest. The results show, I think, that the anticipation was well founded.

II. On the colouring and extractive matters of urine. -Part II

Before entering on a consideration of the analytical details contained in the first part of this memoir, it will be necessary to determine the exact number of urinary extractive matters, the existence of which I am justified in assuming after having brought the examination of their composition to a close. Berzelius, as I have before stated, inferred from his experiments that human urine contained three distinct extractive matters, one soluble in absolute alcohol, another soluble only in alcohol of sp. gr. 0.833, and a third insoluble in alcohol of all strengths, and only soluble in water. A similar conclusion would probably be arrived at by any one perusing the account which I have given of my own experiments without at the same time possessing any information regarding the chemical nature of the com­pounds analyzed. Nevertheless this conclusion would be incorrect, since a few simple experiments suffice to prove that the extractive matter inso­luble in alcohol is not a distinct substance, but invariably contains a quan­tity of alkaline or earthy bases, on the removal of which the organic matter with which they were combined becomes soluble in alcohol, and that the extractive matters peculiar to urine are only two in number, the first being soluble in ether and alcohol, the Second soluble in alcohol only. This inference is quite consistent with the results derived from the analyses of the lead compounds obtained on various occasions from the extractive matter insoluble in alcohol, the details of which have been given in the first part of this memoir. A specimen of the extractive matter insoluble in alcohol was prepared in the following manner:—Ordinary urine was mixed with acetate of lead, and the precipitate thereby produced having been separated, basic acetate of lead was added to the liquid, and the second lead precipitate was filtered off, washed, and treated with dilute sulphuric acid. The excess of the latter was removed by means of carbonate of lead, and the filtered liquid was evaporated to a syrup, which was treated with alcohol. The latter left a portion of the syrup undissolved; and this portion, after being washed with alcohol, was again dissolved in water and sulphuretted hydrogen was passed through the solution, which, after being filtered from the precipitated sulphide of lead, was treated with peroxide of mercury and metallic mercury, for the purpose of removing the hydrochloric acid contained in it. After standing some time and being frequently agitated the liquid was filtered, and sulphuretted hydrogen was passed through it in order to precipitate the mercury in solution, and after being again filtered it was evaporated. The residue left on evaporation was dissolved in a little water, and the solu­tion was mixed with alcohol as long as any precipitate was produced; the precipitate collected at the bottom of the vessel forming a brown glutinous deposit, which, after pouring off the supernatant liquid, was dissolved in water. The solution on being evaporated over sulphuric acid left a residue, consisting of what would be called the urinary extractive matter insoluble in alcohol. It had the appearance of a dark brown, amorphous, brittle, gum-like mass, opaque in thick layers, but translucent at the edges. It had a slightly acid and nauseous taste. It was easily reduced by pounding to a light brown powder, and when exposed to the air it did not appear to deliquesce; but on being afterwards heated in the water-bath it swelled up considerably and became filled with small cavities or vesicles, caused doubtless by the escape of the water which it had absorbed from tho atmosphere. Its watery solution, which was of a dark yellowish-brown colour, had an acid reaction. Its external properties did not differ materially from those ascribed to this substance by Berzelius, who says, “It has a yellowish-brown colour, is opaque in the mass; it has a slightly bitter taste, remains dry in the air, and dissolves in water with a dark yellow colour.”

On a colloid acid, a normal constituent of human urine

In the autumn of 1862, feeling assured that, besides the known normal crystalloid compounds found in urine, this secretion contained colloid substances, I submitted samples of the healthy secretion, after concentration, first, to the process of dialysis, and then to the action of reagents, and finally succeeded in precipitating with alcohol a colloid substance exhibiting a faintly acid or neutral reaction, and containing a small proportion of ash. For a while my endeavours to obtain a definite compound from this amorphous mass were fruitless, until, on observing that basic acetate of lead produced a precipitate in its aqueous solution, I thought of examining this precipitate, and, by decomposing it with sulphuretted hydrogen, found it to consist of an organic acid combined with lead. This new acid is possessed of the properties of a colloid substance; it may be considered as having a definite combining proportion or equivalent weight, and is undoubtedly destined to become of great importance in physiological chemistry.

2. Account of a Repetition of Dr Samuel Brown's Processes for the Conversion of Carbon into Silicon

The authors commenced with an account of the trials they made with the Cyanide of lead; which, according to Dr Brown's most recent announcement, is resolved by his process into gaseous nitrogen and silicon. In the first place, however, they could not succeed in obtaining a pure cyanide of that metal. For whether they decomposed the cyanide of potassium, or the hydrocyanate of ammonia containing an excess of hydrocyanic acid, by neutral acetate of lead, by this salt acidulated with acetic acid, or by tribasic acetate, they constantly obtained a compound containing a large quantity of a hydrated basic acetate of lead; and they were not more successful when they substituted other salts of lead for the acetate as a precipitant, such as the nitrate, basic nitrate, nitrite, chloride, or iodide.