October 14, 1909J 



NA TURE 



475 



derivatives, and support the confirmation previously 

 obtained by Jerusalem by the study of the piciates and 

 styphnatcs. 



The electro-analysis committee (secretary, Dr. F. M. 

 Perkin) reported on experiments upon a new design of 

 potentiomeler, on the general simplification of the 

 apparatus, on a method for the electro-deposition of metals 

 bv means of graded potential, and in connection with the 

 eiectro-deposition of mercury upon gold, silver, platinum 

 and mercury katliodes. 



A joint meeting with the general physics department of 

 Section A took place on Friday, August 27. A large 

 attendance was attracted, and the communications were 

 discussed by members of both sections. Only the more 

 purely chemical papers are noted in the following. Dr. 

 T. M. Lowry presented the report of the committee on 

 dynamic isomerism in the form of a general discussion 

 •on dynamic isomerism in relation to luminous phenomena. 

 Attention was in the first place directed to the decisive 

 evidence adduced that the presence or absence of a band 

 in the absorption spectra of a camphor derivative is in no 

 way dependent on the occurrence or non-occurrence of 

 isomeric change. Certain luminous phenomena, e,g, muta- 

 Totation and phosphorescence, have been shown to be 

 manifest only in presence of a catalyst, and not when 

 pure materials are used ; they are therefore dependent on 

 chemical change. Refraction, dispersion, and opticil 

 rotatory power do not appear to be dependent on the 

 presence of foreign substances, and are to be referred to 

 physical characteristics of the molecule. Colour, fluores- 

 cence, and triboluminescence are still subjects of con- 

 troversv. The last two are probably dependent on chemi( ;il 

 structure, but it is difficult to resist the conclusion that 

 ■colour is an essentially physical phenomenon in which 

 chemical change plavs no essential part. The conclusion 

 is one which is confirmed by the study of crystallisation in 

 relation to phenomena. 



This paper provoked considerable discussion. Sir J. 

 Larmor remarked tliat phosphorescence is due, not to the 

 formation of ions, but to complex molecules forming and 

 ■breaking up, and instanced that iodine vapour, which is 

 strongly phosphorescent, shows no conductivity, and there- 

 fore contains no ions. 



In three further notes Dr. Lowry put on record some 

 useful improvements in the technique of optical investiga- 

 tions. Measurements of rotatory dispersion have been 

 made with light of twenty-si.x different wave-lengths, and 

 the green mercury line Hg 5461 has been selected as the 

 principal standard in place of the sodium doublet on 

 account of its brilliance and purity. 



The optical and magnetic dispersions produced by 

 quartz are identical, but optically active liquids have the 

 optical dispersion usually, though not always, highqikthan 

 the magnetic dispersion. It is suggested that the magnetic 

 rotatory power of liquids depends upon a spiral packing 

 of the molecules of the same general character as that 

 which produces the optical rotatory power of quartz. 



To produce a cadmium spectrum of sufficient intensity 

 for polarimetric work, use is made of the silver cadmium 

 alloys ; these have high melting points, and give a steady 

 arc which can be kept true to centre by rotating the 

 electrodes in opposite directions. The silver and cadmium 

 lines are so far separated that no overlapping takes place 

 even when the spectroscope slit is opened to its full width. 

 Mercury and cadmium lines are suggested as standards 

 in refractometry. 



Two papers by Dr. C. J. J. Fox were taken as read. 

 The constancy of the hvdrogen-gas electrode In sulphuric 

 and hydrochloric acids has been investigated when gold 

 or platinum coated with either platinum or palladium 

 1)lack are employed ; in a very few minutes values con- 

 cordant to less than o-oi; of a millivolt were obtained. 

 Palladium coated with palladium black gave a value 4 to 

 5 millivolts too high. .\ new method of preparing trust- 

 worthy mercurous sulphate for standard cells is described ; 

 this consists in heating commerciallv pure mercurous 

 sulphate for a day or so at i2o"-i5o° in a sealed tube 

 with a little mercury and dilute sulphuric acid. The 

 sulphate is thus obtained free from nitrate and basic 

 sulphate. 



The joint discussion with the botanists and agriculturists 



NO. 2085, VOL. 81] 



on wheat and flour had been carefully organised previous 

 (o the meeting, so that the contributions might be made 

 m logical sequence and present as full a picture as possible 

 of the exact position of our present knowledge of wheat 

 and flour from every point of view. The present problems 

 are quite clear; the chemist has to map out the wheat 

 soils and to watch the quality of the product ; the botanist 

 has to breed wheats that suit local requirements and com- 

 mand a good price in the market. 



The subject was particularly appropriate for discussion 

 at Winnipeg, and the discussion, which throughout was 

 very technical in character, was closely followed by an 

 expert audience. The first paper, by Dr. Stapf, on the 

 history of the wheats, dealt with their classification 

 and characteristics. The great economic importance of the 

 wheats proper lies in the fact that the looseness of the 

 grain in the husk enables threshing to be quickly and 

 cheaply accomplished. Dr. E. J. Russell followed with a 

 paper by .'\. D. Hall and himself on the factors deter- 

 mining the yield of wheat, based on the experiences at 

 the Rothamsted Station since 1851. The chief elements 

 of nutrition derived from the soil or manure are nitrogen, 

 phosphoric acid, and potash ; other elements also play 

 their part, but are supplied in sufiicient quantity by all 

 ordinary soils. The yield of grain is proportional to the 

 nitrogen supplied, but two sets of factors may be traced 

 in the results. At first the root system of the plant in- 

 creases with the supply of nitrogen, and the yield is more 

 than proportional to the supply ; subsequently other limit- 

 ing factors come into play, and the increase is smaller 

 for the third and fourth increments of nitrogen. 



Wheat does not require large quantities of phosphoric 

 acid ; the effects of this manure are secondary, and 

 dependent upon season. A deficiency of potash is shown 

 by a reduced yield, especially in dry seasons, and by in- 

 creased tendency to disease, rust, &c. 



Wheat is one of the crops best adapted to dry regions. 

 High temperatures are not necessary excepting at the time 

 of maturation. The type of soil in relation to climate 

 is a very important factor. To each type there is a limit- 

 ing yield, beyond which the crop will not go. This 

 limit is not the same for all varieties of wheat. 



Mr. F. T. Shutt, chemist to the Dominion Experimental 

 Station, Ottawa, followed with an account of the influence 

 of environment on the composition of wheat. The_ factors 

 which might be supposed to influence composition are 

 hereditv, environment and soil. Soil, however, has very 

 little effect on the composition, as distinct from the yield, 

 of wheat. The shorter the period which elapses from the 

 formation of the kernel until it is ripe the higher the 

 nitrogen content. High temperatures, long days, and 

 absence of excessive moisture during the ripening process 

 hasten the maturation of the grain and increase the per- 

 centage of gluten. These are the conditions which prevail 

 in the Canadian North-west. 



Experiments were described in which the same wheat 

 was grown on old land and recently cleared land, the 

 older land being the drier and yielding wheat with a 

 higher percentage of protein. It is suggested that the 

 quality of the wheat as measured by the quantity of 

 gluten it contains is dependent on the amount of soil 

 moisture during development and ripening of the grain. 

 The quality of the gluten, however, is considered to he 

 controlled by heredity. 



The subject was next developed from the point of view 



of the miller, a paper by Mr. K. E. Humphries being read 



by the recorder of the section. This dealt with the vexed 



question of quality in wheaten flour. Good quality is the 



sum of excellence on several points, and is tpchnically 



denoted by the term " strength." Strength is defined as 



the capacity for making large, shapely, and therefore well 



aerated loaves. This is a very complex conception ,_ and 



it is now admitted that at least five separate considera- 



j tions are included in the term quality ; these are 



I (i) flavour; (2) colour; (3) stability of dough; (4) size 



, and shape of loaf ; (5) yield of bre.ad per sack of flour. 



\ pleasant flavour is an essential, but the exact flavour 



desired is chiefly influenced by fashion. Colour in bread 



\ is largely a question of optics, a strong flour making 



I a whiter loaf than a weaker flour. A large loaf indicates 



a high gas-making capacity and a high diastatic power, 



