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After a brief description of a new apparatus for the determination of heats of combustion, the theory of an isothermally jacketed calorimeter is discussed. Several factors which require attention in accurate determinations are dealt with, viz.: purity of reagents, completeness of the combustion reaction, determination of time, determination of weight and corrections of the second order. A description is then given of some details of the apparatus and method. The accuracy attained, 0.01-0.02%, is demonstrated in a series of experiments. Finally, it is shown that the heat of combusiton of our sample of benzoic acid is in excellent agreement with that of preparation 39b of the National Bureau of Standards, Washington.

In a previous communication 1 ), the hydrolysis of cis- and trans-1:4-cyclohexane-di-tritylether with hydrochloric acid in water and propanone. is described. In order to confirm the results obtained in that paper, a method has been worked out, by which these ethers are quantitatively decomposed by treatment with dry hydrogen chloride in anhydrous benzene or chloroform solution. The diols separate as hydrogen chloride addition compounds (with benzene of crystallisation), which dissociate completely in the solid state. The 1:4-cyclohexanediol preparations obtained by both these methods, were absolutely identical. There appears to be no conversion of cis trans or vice versa in these reactions. The cis-diol is converted at 101°. 4 into a liquid crystalline phase, melting at 113°.0. The first process requires about four times as much heat as the second.

In guter Ubereinstimmung mit dem fruher fur die Aktivierungsenergie der Dissoziation des sym. Tetra(2,6-dimethylphenyl)athan in ortho-Dichlorbenzen gemessenen Wert von 22.5 kcal wurde in den Losungsmitteln ortho-, meta- und para-Xylen 22.9 bzw. 23.0 bzw. 23.4 kcal gefunden.

The energy of activation (E), the Arrhenius constant (A) and the period of half-life at 80° (t1/2) for the radical-dissociation reactions of the following compounds: pentaphenylethane (I) 1,1,1,2-tetraphenyl-2-(2-methylphenyl)ethane (II) 1,1,1,2-tetraphenyl-2-(3-methylphenyl)ethane (III) 1,1,1,2-tetraphenyl-2-(4-methylphenyl)ethane (IV) 1,1,1-triphenyl-2,2-di-(3-methylphenyl)ethane (V) 1,1,1-triphenyl-2,2-di-(4-methylphenyl)ethane ((VI) have been calculated from the velocity constants for the first-order reactions of the radicals concerned with oxygen in o-dichlorobenzene as a solvent

Au cours de la separation des cyclohexane-1,3-diols obtenus par reduction catalytique du resorcinol par la voie des ethers ditrityliques, il s'est produit des complications que Lindemann et Baumann n'ont pas decrites. Le perfectionnement du procede mena au diol-cis a point de fusion de 83°, l'isomere trans fondant a 117°. La meme methode, appliquee au melange de diols obtenu par hydrogenation du quinol sans dissolvant, fournit les deux cyclohexane-1,4-diols isomeres a un etat tres pur. Il fut constate que les isomeres fondaient respectivement a 112 et 143°. Pour l'analyse thermique furent determinees les courbes de fusion des systemes 1,4-diol cis et trans, 1,4-diol-ditritylether cis et trans, et 1,4-diol-diacetate cis et trans du cyclohexane. Ces diagrammes ont montre que le compose a point de fusion de 100-102° prepare selon von Baeyer, lequel jusqu'ici passait pour le cyclohexane-1,4-diol-cis a l'etat pur, est en realite un melange d'environ 84% de cis- et de 16% de trans-1,4-diol. De meme le diacetate du cyclohexane-1,4-diol-cis de von Bayer contenait 17% de l'isomere trans.

The theoretically possible conformations of a substituted diphenylacetic acid and their interconversions are discussed. The activation parameters for the racemization of a series of ortho-alkyl-substituted diphenylacetic acids are determined.

Grignard compounds, prepared in benzene in the presence of one molar equivalent of an ether derived from (-) (S)-2-methylbutan-1-ol, yield optically active alcohols on reaction with aldehydes. A comparison is made with the optical activities of the products obtained when an optically active bifunctional ether ((+) (2 R:3 R)-2,3-dimethoxybutane) is used. A discussion is given of the reacting system.

A new method is described for investigating the osmotic situation of nonvolatile compounds in various solvents with a concentration limit as low as about 10−3 mole/1. The method is based on measuring as a function of time the loss of weight of an evaporator made of porous material wetted with the pure solvent, hanging in the vapour of the solution under investigation. The gas-free solution is injected by its own vapour pressure through a crystal-seal in an evacuated glass apparatus, having no ground joints or valves. Calibration data are given.

Purification of the cyclanes with 4 to 9 C-atoms was effected by fractional distillation. Progress of the purification was checked with the aid of melting curves of the fractions (heat content vs. temperature curves of the melting process). The impurity content of the final samples is estimated at less than 0,2%. A fractionating column with a rotating cylinder and a small calorimeter for measurements on melting and transition processes at temperatures from — 180° to +70° are described.

The series of the normal saturated fatty acids and their methyl esters with 5 to 20 carbon chain atoms was synthesized and careful purified, mainly by fractional distillation of the methyl esters in columns with up to 58 theoretical plates. The purity was checked with the aid of melting curves determined in a microcalorimeter and proved to be 96.6% or better. Refractive indices were determined and can be represented by with an accuracy of 5 units in the fifth decimal place (c = number of carbon chain atoms). Densities, accurate to 1 unit in the fourth decimal place, can be represented by Boiling points can be given by b.pt. 20 mm for the methyl esters (c> 5), accurate to 0.1 °. From our data, combined with literature values, the molecular refractivity of the CH2 group in an aliphatic chain calculated according to Lorentz-Lorenz. was determined at 4.64 at room temperature. In addition, melting and transition points, and heats of fusion and transition were determined.

The heats of combustion of some samples of pure benzoic acid, partly supplied by the National Bureau of Standards (Washington) and partly prepared by the authors, have been carefully measured by reference to electrical standards. The mean value of the absolute heat of combustion of benzoic acid under standard bomb conditions in some series of determinations carried out in the years 1946-1948 is 26438 ± 4 j/g. New determinations in 1954 showed a mean value of 26435 ± 4 j/g.

An adiabatic calorimeter has been developed for the measurement of the heat of solution. By means of a thermistor temperature changes of about 0.04°C can be measured with a precision better than 4 × 10−5° C, hence only small amounts of solute are required. As a check of accuracy the integral heat of solution of KCl in H2O at 25°C up to a concentration of 2 × 10−4 molar was directly determined as 17.24±0.03 kj per mole1 ).

The heats of combustion, melting points, heats of fusion, boiling points, refractive indices and in four cases the densities have been determined on selected samples of the cyclanes with 4 to 9 C-atoms; some hitherto unknown transition points were discovered and the heats of transition measured. The heats of vaporisation at 25° are estimated. Results of the measurements are discussed.

The heats of solution of 18 alkali halides in anhydrous formamide at concentrations of about 0.01 molal and at 25° have been measured with an adiabatic calorimeter. Some physical properties of formamide have been determined. By applying the extended Debije-Huckel theory the enthalpies of solution at infinite dilution were calculated. The difference in enthalpies of solution of the fluorides, chlorides, bromides and iodides, respectively, in water and in formamide appeared to be a constant, independent of the cation. An explanation in terms of van Eck's theory of ionic solvation is given.

Accurate heats of combustion of the title compounds were measured in an electrically calibrated calorimeter; the liquid samples were burned in Pyrex ampoules; the water content in the samples was titrated by the Karl Fischer method. The increment of the standard enthalpy of combustion, -ΔHR25liq. (=-ΔHC0liq.) for one CH2 group in the chain proved to be 653.8 kj/mole for both the acids and the methyl esters studied, which is the same value as determined for the liquid paraffins. The following formulae, in which c = the number of carbon chain atoms (c > 5) can be used to calculate the standard enthalpies of combustion (based on the 1951 atomic weights): -ΔHliq. = 653.8 c − 430.2 kj/mole for the acids, accurate to 0.03 − 0.04%, -ΔHliq. = 653.8 c + 292.6 kj/mole for the methyl esters, accurate to 0.02%. The theoretical heat of esterification of a fatty acid with methanol at 25 °C, disregarding heats of solution and dilution, was calculated to be 3.8 ° 0.6 kj/mole, which can be compared with the value of 4.2 ° 0.3 kj/mole for the theoretical heat of esterification of acetic acid with ethanol at about 20 °C, determined directly by Mme Berenger-Calvet.

The heats of combustions of all the phenylethenes except styrene 1 ), were measured. The values (UR) given in the table below refer to the isothermisochore reaction: CmHn + (m + 1/4 n) O2 m CO2(g) + 1/2 n H2O(l) at 30 atm O2 and 25° C.

After a discussion of the requirements to be met by the method of stirring used in liquid calorimeters for accurate heat measurements, a description is given of a calorimeter constructed on a new principle. The development of heat occurs in a cylinder which is somewhat smaller than the calorimeter vessel. Water is circulated between the two walls, where the thermometer is placed by means of a centrally fixed centrifugal pump. In this way, the actual wall temperature of the calorimeter-vessel is measured; this is essential for the accurate calculation of the “radiation” correction. A simple method is described for determining the heat due to stirring. Finally, the required minimum duration of the main period is discussed.

A method for the gradual decomposition by oxidation of fatty acids into their next lower homologues is described and tried on palmitic and stearic acids. The new method comprises the following steps: bromination of the original fatty acid in α-position, conversion into α-hydroxy-fatty acid, oxidation of the latter to aldehyde with lead tetra-acetate and subsequent immediate oxidation of the aldehyde to the desired lower fatty acid with air and an excess of lead tetra-acetate. The various steps of the first reactions are executed in such a manner, that nearly quantitative yields are obtained. The decomposition of the α-hydroxy-fatty acid to the lower fatty acid gives a yield of 88 to 89%. The total yield of lower homologues was approximately 84%.

The integral heats of solution of some samples of potassium chloride have been measured carefully with an adiabatic calorimeter. The results indicate that it is necessary to revise the value of the heat of solution of potassium chloride in water.

A method is described for filling thin-walled ampullae with volatile liquids with the total exclusion of air and water. In this way it is possible to weigh out accurately the amount of material used for a heat of combustion measurement before the experiment is made. To aid the combustion reaction in proceeding to completion a high platinum crucible is used covered with a platinum shield. In a normal heat of combustion reaction it is impossible to detect the presence of carbon monoxide in the combustion gases. The reproducibility obtained is 0.01-0.02%.

In order to be able to calculate readily the so-called “radiation” correction in calorimetric measurements, the jacket-temperature must be kept constant and the contents of the calorimeter vessel must be stirred at a constant speed. This article describes a thermo-regulator for this purpose, in which the fluctuations are not greater than 0.002°. For every calorimeter used for accurate work, it is desirable to investigate beforehand whether the heat exchange between the vessel and the jacket satisfies Newton's equation. With the help of recent data it has been investigated how wide the air layer may be before convection occurs. This is necessary in order to obtain a system which satisfies Newton's equation. Finally, various methods of approximation for calculating the “radiation” integral are discussed.