658 



NA TURE 



[May 20, 1922 



were taken from Mount Wilson and other heights. 

 A cumulus formed by convection over fire is exceed- 

 ingly good, and several lenticular cloud specimens are 

 of interest ; types are given of the funnel cloud or 

 tornado cloud. The height of clouds is discussed, and 

 it is said that they are lower during winter than 

 during summer, due to the difference in relative 

 humidity. The extension of our knowledge of the 

 upper air has added much to the better understanding 

 of cloud development. 



Electrolytic Dissociation. — The Journal of the 

 American Chemical Society for April contains an 

 interesting paper by Prof. T. W. Richards and A. W. 

 Rowe on the heats of neutralisation of alkalies with 

 monobasic acids at various dilutions. As is well 

 known, the approximate equality of the heats of 

 neutralisation of strong acids by strong bases, 

 indicating that the same reaction took place in all 

 cases, namely, the union of hydrogen and hydroxide 

 ions to form undissociated water, was one of the 

 strong arguments for the theory of electrolytic 

 dissociation put forward by Arrhenius. The careful 

 measurements described in the paper show that the 

 heats of neutralisation are slightly different, but since 

 they all tend to the same limit with increasing dilution 

 this is almost certainly the result of slight differences 

 in the extent of ionisation of the different acids, 

 bases, and salts. In solutions containing 100 grm. 

 molecules of water to one of acid and base, the 

 heats of neutralisation varied from 13-75 to 14-09 

 kilogrm. -calories. The heat of formation of water from 

 its ions is found by slight extrapolation to be 13-62- 

 13-69 kilogrm. - calories at 20°, in good agreement 

 with the value 13-7 adopted by Arrhenius. These 

 results would seem to rule out the assumption made 

 by Ghosh and others that these electrolytes are all 

 equally dissociated at the same dilution, and in a 

 paper in the same journal by Prof. J. Kendall the 

 theory of Ghosh is also adversely criticised from other 

 points of view. 



The British Beet-Sugar Industry. — In 1745 

 the Berlin chemist Margraaf discovered sugar in the 

 beet, and in 1812 Napoleon laid down 75,000 acres for 

 the cultivation of beet and established six centres of 

 instruction. This was the result of the Continental 

 blockade. Immediately before the outbreak of war 

 in 1914. France and the United States each had half 

 a million acres under sugar-beet, Germany had a 

 million acres, and Austria, Belgium, Denmark, and 

 Holland also made important contributions to the 

 industry. Great Britain had only one factory, at 

 Cantley in Norfolk, under Anglo-Dutch control. 

 In the Journal of the Society of Chemical Industry 

 for April 15 an account, with excellent illustrations, 

 is given of the beet-sugar works at Kelham, Notts, 

 owned by Home-Grown Sugar, Ltd. This works, 

 which was designed by a French firm, and is almost 

 entirely staffed by French workmen and managers, 

 was the result of a grant of money from the Treasury. 

 Up to date there has been a large deficit on the working 

 of the factory, but as a result of the arrangement 

 with the Government to remit the duty until the 

 company is in a position to produce a total of 

 50,000 tons of sugar a year, it is hoped that progress 

 will be made. The process is identical with that 

 used in the North of France. Sugar-beet has been 

 cultivated on 230 acres, and some 2300 acres have 

 been grown locally by farmers, an average of 5-5 

 acres each. The sugar content of the roots has 

 reached 15-92 per cent. The roots are washed, sliced 

 mechanically, and treated with water in diffusion 

 apparatus at about 70° C. The extract contains 

 about 12-5 per cent of sugar, and the residue, after 

 drying and mixing with molasses, is sold for stock 



NO. 2742, VOL. 109] 



feeding. The aqueous extract is treated with milk 

 of lime and then with carbon dioxide to precipitate 

 the lime. The clear liquor, after filtration, is treated 

 with sulphur dioxide, evaporated in vacuo, cooled, 

 and the crystals drained in centrifugal machines. 



A New Desensitiser. — We learn from the British 

 Journal of Photography of May 5 that Dr. E. Konig, 

 of the Hoechst firm of Meister, Lucius, and Briining, 

 who was associated with Dr. Liippo-Cramer in his 

 work on desensitisers of photographic emulsions, has 

 continued the work on this subject. The practical 

 result is that he has obtained a desensitiser fully equal 

 in its effects to phenosafranine and without some of 

 its disadvantages. The new desensitiser is called 

 " Pinakryptol " and is a greenish-grey mixture of two 

 desensitisers. One part is dissolved in 5000 parts of 

 water for use, and its notable advantage is that it has 

 no staining action on gelatine or celluloid or the fingers 

 or nails of the user. 



Petrological Microscopes. — We have received 

 from Messrs. James Swift and Son, Limited, a cata- 

 logue of their petrological microscopes. The excel- 

 lence of their work has earned them a well-deserved 

 reputation which is still maintained. A number of 

 types are described in the catalogue, some with a 

 rotating stage and others with rotating nicols as 

 originally designed for the firm by Mr. Dick. The 

 former include the " Primex " for the use of element- 

 ary students, the " Advanced Student," the " Petros," 

 and the "Survey." The "Petros" has a hinged 

 analyser, which can be brought into position above 

 the ocular. This has the advantage that a quartz- 

 wedge can be introduced in the focus of the ocular. 

 In the remainder the analyser is inserted in the lower 

 end of the body tube, but a second analyser, which 

 can be placed above the ocular, can be purchased as 

 an accessory. In the " Advanced Student " the 

 convergent system fits into a sleeve above the 

 polariser, but the top lens can be removed if a less 

 convergent system be desired. This arrangement can, 

 however, be replaced by the convenient swing-out 

 screw focussing adjustment which is fitted to the 

 more expensive "Petros" model. The "Survey" is 

 distinguished by its well-equipped substage. In all 

 except the " Primex " there are two Bertrand lenses for 

 the observation of interference figures, one at the 

 upper end of the tube for measuring comparatively 

 small crystals, and the other just above the objective, 

 giving a much larger image. A more advantageous 

 course is to employ, instead of a Bertrand lens, an 

 auxiliary lens above the ocular. The light coming 

 from a small crystal or part of a crystal, which it is 

 desired specially to examine, can first be isolated by a 

 perforated diaphragm in the focus of the ocular and 

 the auxiliary lens then placed in position, when the 

 interference figures can be observed unaffected by 

 extraneous light. This procedure was recommended 

 by a committee of the British Science Guild, and 

 excellent auxiliary lenses of this description have 

 been prepared by Messrs. Swift, which might have 

 been expected to have had a place in this catalogue. 

 Two types of microscope with rotating nicols are 

 described, the well-known " Dick " microscope, and 

 the " Grabham-Dick," distinguished by the triple nose- 

 piece beneath the stage, which makes it possible to 

 place three different types of condenser in position 

 in turn. Full particulars are given, in the concluding 

 pages of the catalogue, of different objectives, nose- 

 pieces, centring objective changes, and other necessary 

 or commonly employed accessories manufactured by 

 the firm. It should have been stated in the case of 

 quartz-wedges whether they are graduated to show 

 the relative retardation at different points. 



