Showing papers by "Ministry of Supply published in 2007"

A systematic assessment of dissolved oxygen supply in a 20-litre culture vessel

Abstract: The factors influencing aeration are discussed and, using the sulphite oxidation method of measurement, the influence of impeller diameter and speed, air rate, and air pressure on the aeration efficiency of a 20-litre culture vessel has been determined and the power consumed by the impeller measured. Conditions are given for obtaining sulphite oxidation rates of 200–250 millimoles of O2 per litre of medium per hour which can be increased to 500–600 millimoles by raising the operating gauge pressure from zero to 1·36 atm.

The effect of oxygen supply on the rate of growth of aerobacter cloacae

Abstract: A simple theoretical treatment is given of the effect of a limiting oxygen supply on the growth of bacteria. Results are given for the batch culture of Aerobacter cloacae. Using different levels of aeration, the growth rate was measured when growth was restricted by oxygen supply. The bacterial concentration at which restriction occurred was also determined.

Vapour pressures of some rare‐earth halides

Abstract: Approximate data are given on the vapour pressures, in the range 10−1 to 10−3 mm. of mercury, of many of the cerium group of rare-earth halides. The vapour pressures were determined by the method of molecular effusion. Also, a method is described for dehydrating these halides such that in their anhydrous form they are free from any basic salts and are 100% volatile in vacuo.

The protective properties of various phosphate coatings on steel

Abstract: Coatings of iron, manganese and zinc phosphates formed on steel by representative industrial immersion processes are compared, with special reference to their value in the prevention of rasting. The results are examined in the light of the thickness, composition and wear resistance of the coatings. Protective properties are relatively well developed in manganese phosphate coatings, but, since phosphating in practice normally constitutes only a part of a protective system involving organic coatings, iron and zinc phosphates can give adequate results in appropriate systems. A recent spot-test of Russian origin, although at present not sufficiently well developed for inspection purposes, is likely to provide a useful additional tool for examining coatings. Variations in the coatings, in particular those that occur in the working range of a plain manganese phosphate process, have been examined and one untoward effect was identified, that due to adventitious copper contamination of the bath.

Analysis with double‐beam infra‐red spectrometers

Abstract: A number of applications of balanced double-beam systems are described and their special advantages discussed. Such methods have been used for the qualitative study of oils and paints and for the detection and identification of materials separated in chromatographic columns or on specially prepared paper chromatograms. Applications of such methods to quantitative analysis are also discussed and are illustrated by examples of analyses of cordites and lubricating oils. There are indications that the behaviour of oils undergoing oxidation can be followed in this way.

Formaldehyde condensations with phenol and its homologues. XIV The dehalogenation of phenolic alcohols having halogen substituents in the nucleus

Abstract: A major obstacle in the chemistry of phenolic resins is the difficulty in preparing some of the simple phenolic alcohols, owing to their reactivity and the formation of isomers which are not readily separated. The use of halogenated phenols, in which one or more of the free reactive nuclear positions are blocked by halogen atoms, generally avoids both further reaction and the formation of isomers. If a simple means existed of removing the halogen from alcohols prepared from such halogenated phenols, under mild conditions which would not cause further reaction of the product, then a method would exist for the preparation of many phenolic alcohols which cannot be prepared by the direct reaction of formaldehyde and the appropriate phenol. It has now been shown that this process can be accomplished by the use of Raney alloy in the presence of aqueous sodium hydroxide. A new alcohol of phenol (2:6-dihydroxymethylphenol) has been prepared by this means.

The correlation of explosive power with molecular structure

Abstract: The relationship of oxygen balance to explosive power as measured by the ballistic mortar has been studied empirically. Starting from the modified oxygen balance developed by the authors for detonation velocity calculations, a numerical measure called the ‘power index’ has been derived which correlates closely the features of molecular structure with the power values. Explosive power has also been expressed as an additive function of details of molecular structure. This has been made the basis of a method whereby power values may he derived which agree with experimental results to about 5% and which provides a rapid alternative to the thermochemical calculations which result from normal theoretical treatment.

A physical method of analysing sulphur dichloride

Abstract: A physical method of analysing samples of sulphur dichloride is described. It required the determination of density to 0·0001 g./ml., and of refractive index to 0·0001. Density was found by means of a submerged float with an iron core, and refractive index by a protected critical-angle refractometer. The properties of sulphur dichloride and of sulphur monochloride were as follows: By determining the densities and refractive indices of mixtures of the two chlorides with each other and with chlorine, a nomogram was constructed that related the percentage of sulphur monochloride and of chlorine, in any preparation of sulphur dichloride, to its density and refractive index. The analysis, accurate to 0·2% of each impurity, could be carried out in 15 minutes.

The surveillance of cinematograph record film during storage

Abstract: A number of cellulose nitrate-base cinematograph films have been examined, many of which are twenty or thirty years old. Reactions between decomposition products of the base and gelatin had in some cases caused the emulsion layer to become sticky with loss of the contained silver image. Since films in this condition cannot be duplicated, it represents a total loss of record. This can now be avoided by subjecting the film to certain tests, the results of which give adequate warning of the onset of the critical stage, thereby enabling the film to be duplicated while still in good physical and optical condition. The application of these tests has been incorporated in a scheme of surveillance devised for use with stored film.

Formaldehyde condensations with phenol and its homologues. XI. The preparation of 2‐hydroxymethyl‐3:5‐dimethylphenol by a new general method

Abstract: In Part V of this series, it was shown that the reaction of formaldehyde with 3:5-dimethylphenol could result in the formation of either the p-monoalcohol or the 0-0′-dialcohol, according to the reaction conditions. The 0-monoalcohol (2-hydroxymethyl-3:5-dimethylphenol) has now been prepared from 2-dimethylaminomethyl-3:5-dimethylphenol by conversion with acetic anhydride to 1-acetoxy-2-acetoxy-methyl-3:5-dimethylbenzene, followed by reduction of the latter with lithium aluminium hydride. This process may be expected to provide a general method for the preparation of phenolic alcohols from the parent phenols. The structure of the 0-alcohol has been confirmed by reduction of the corresponding aldehyde with lithium aluminium hydride.

Design of packed distillation columns. III. Rectification film resistances in a packed column

Abstract: Data are presented which lead to the conclusion that the liquid-film resistance was the controlling resistance in rectification of a binary system carried out in a particular packed column. This confirms the conclusion reached by other workers on similar packed columns.

The freezing and melting of some sulphur chloirdes

Abstract: Freezing and melting curves were obtained for pure sulphur dichloride and pure sulphur monochloride, and for mixtures of the two. Because the mixtures contained very little free chlorine, the usual deposition of higher chlorides did not obscure the phase behaviour, which showed that the following compounds were stable at low temperatures: SCl2, freezing and melting at 151° K.; S2Cl2, freezing and melting at 191° K.; and an intermediate compound, probably S2Cl3, freezing and melting at 145°k. No compound corresponding to S3Cl4 was indicated; all mixtures containing from 20% to 50% of sulphur dichloride showed a rapid fall in temperature during freezing. The phenomena associated with the freezings are described; and evidence for the formation and persistence of the intermediate compound at room temperature is discussed.

Formaldehyde condensations with phenol and its homologues. XIII.The relative reactivity of the ortho AND para Positions in the formation of alcohols of substituted phenols

Abstract: In earlier papers of this series it has been shown that the action of formaldehyde on 3 : 5-xylenol in the presence of sodium ethoxide catalyst results in the formation of an ortho-ortho-dialcohol. Attempts to prepare as ortho-monoalcohol by modification of the reaction conditions foiled. A consideration of the behaviour of other substituted phenols appears to lead to a generalization that when both meta positions and sometimes when the para position of phenols, relative to the phenolic hydroxyl group, are occupied by substituents, the introduction of a methylol group into one ortho position results in an enhanced reactivity of the other. Such an enhanced reactivity of one ortho position would explain why dialcohols are readily formed, but that the presumably intermediate mono-alcohol cannot be isolated. Attempts to prepare some trinuclear substituted compounds by condensation of di-ortho-substituted phenols with various intermediates failed. The explanation of this failure is probably due to a decreased reactivity of the para position in these di-ortho-substituted phenols.

A note on the correlation of flooding rates for packed gas‐liquid columns

Abstract: The following equation, which is derived from an expression previously obtained for liquid-liquid extraction columns by Dell & Pratt (1951), and which is basically similar to the equation of Bertetti (1942), is proposed for the correlation of flooding rates for packed absorption and distillation columns: This equation can be reduced to a form resembling the graphical correlation used by Sherwood, Shipley & Holloway (1938). A comparison with the available experimental data shows that agreement is good up to a critical value of the group on the right, beyond which the exponent changes sharply to to − 0·20. Derived values of the constants C2 are given for four types of packing, and the applications and limitations of the equation are discussed.

Design of packed distillation columns. II. Operating vapour rates for packed distillation columns

Abstract: Relatively simple correlations of the important variables associated with allowable vapour rates in packed columns are presented. These are similar to those already used for the same purpose in connexion with plate columns. The suggested method of calculation of limiting velocity is simpler than those methods derived from correlations of a more complex type which are described in the literature on packed columns; it is nevertheless adequate for preliminary design of columns operating at atmospheric pressure or below.

Performance of climbing film evaporators

Abstract: Performance data for three sizes of climbing film evaporator processing organic liquids are presented. The general trend of the quantitative measurements suggests the existence of a critical operating temperature difference to obtain a maximum performance. General observations of practical design value are offered.