October 6, 1898] 



NATURE 



557 



copal varnish, turpentine, drying oils, essentia! oils and metals 

 on a photographic plate, in the dark, and detailed his method of 

 experiment. Actual contact is not necessary to obtain the 

 action ; it takes place also at a distance. The time required is 

 dependent upon the temperature ; in the earlier experiments 

 it required a week to produce a developable image, but by 

 raising the temperature to 55° C. considerable action was 

 recorded in five minutes. Sheets of gelatine, celluloid, gutta- 

 percha and collodion do not hinder the action, when placed as 

 screens between the active surface and the plate. Hydrogen 

 peroxide is regarded by Dr. Russell as most probably the 

 active agent in all these actions, but further experiments are in 

 progress to decide this more definitely. In a complementary 

 paper by Mr. C. H. Bothamley, on " The action of certain 

 substances on the undeveloped photographic image," evidence 

 was adduced to show that printer's ink can after a time act on a 

 photographic plate and destroy the " latent image." The 

 vapour of hydrogen peroxide and turpentine have the same 

 effect. Whereas, therefore, hydrogen peroxide acting for a 

 short lime or in small quantity produces a developable 

 image, by more prolonged action or in a more concentrated 

 form it acts as an oxidiser and destroys the image. Probably 

 both actions take place simultaneously, and the result at any 

 given instance depends on their relative rates. Prof. Percy 

 Frankland contributed an additional photographic action — that 

 of bacteria. By placing gelatine cultures of Bacillus coli com- 

 munis and of Proteus vulgaris, either in juxtaposition or at a 

 distance of half an inch from a photographic plate, definite 

 developable images were obtained. The action is stopped by 

 glass or mica, and is therefore not due to radiation, but to the 

 evolution of some volatile matter which reacts with the plate. 

 Bacterial growths which are luminous in the dark (Photo- 

 bacterium phosphorescens) have a still greater action. The 

 investigation is to be extended to other organic structures 

 vegetable and animal, living and dead. Amongst these 

 contributions may be included an account by Dr. J. H. 

 Gladstone and Mr. Hibbert of their further work on " The 

 absorption of the Rcintgen rays by chemical compounds," which 

 dealt chiefly with their attempts to perfect quantitative methods 

 of estimating the comparative densities of their radiographs. 

 Mr. Hibbert also described an instrument he had devised for 

 ascertaining the relative grades of the Rontgen rays. 



Applied chemistry received attention under various headings. 

 Special local interest naturally centred in Dr. J. Gordon Parker's 

 paper on " Recent advances in the tanning industry," in which the 

 lack of scientific methods amongst the tanners of this country 

 was sternly criticised. Dr. Parker referred to the employment 

 of extracts in tanning as a marked advance which had also 

 brought about improved methods of estimating the tanning value 

 of the materials employed in the industry, but bateing and 

 " puering"of hides by means of dog and hen excrement was stig- 

 matised as a standing disgrace to the; leather trade. American 

 and continental tanners appear to be far ahead of their English 

 brethren in respect to the extraction of tanning materials in the 

 tanyard. The cold extraction processes employed here mean 

 loss and waste. Analyses of over 300 samples of so-called waste- 

 spent tan from forty tanyards in (ireat Britain having shown an 

 average of over 9 per cent, of available tannic acid. With 

 valonia alone this represents a loss of i/. 13^. 4<f. a ton, about 

 500,000/. annually. In Germany and America warm extraction, 

 which means practically complete extraction, has proved suc- 

 cessful. The fear of darker colour in leather from the use of 

 warm extracts is much exaggerated ; as the temperature of ex- 

 tracting is raised, more colouring matter is dissolved, but it is 

 difficultly soluble, and much of it is re-deposited on cooling. 

 Mr. Vernon Harcourt exhibited and described his new " 10- 

 candle pentane lamp," which was most favourably commented 

 on by Prof. Vernon Boys as a standard of light. Mr. Vernon 

 Harcourt pointed out the advantages of a 10 or i6-candle standard 

 for testing illuminating gas, over that now employed, and also 

 the nee(;l of a large but compact standard flame. The burner is 

 supplied with a mixture of air and gaseous pentane from a 

 reservoir placed on a bracket at the top of the lamp. As this 

 mixture falls down a siphon tube connecting the reservoir and 

 the lamp, fresh air enters the former, which is provided with 

 cross partitions, causing the air to travel backwards and for- 

 wards over the surface of the pentane and to mix with a pro- 

 portion of pentane, which varies in amount with the external 

 temperature. The arrangement of the lamp is such, however, 

 that the variation in the proportion of pentane does not affect 



NO. I 5 10, VOL. 58] 



the output of light. There is a casing round the burner with a 

 conical top which steadies the flame, the upper part of which is 

 drawn together in a long brass chimney which cuts off the light 

 of this part of the flame. The lamp is so constructed that a 

 cool air current issues through the middle of the argand burner, 

 which thus gives a steady flame 60-70 mm. high, having an 

 illuminating value of rather more than ten candles. By adjust- 

 ing the tube which receives the top of the flame at a height of 

 47 mm., the light shed horizontally is reduced to exactly 

 ten candles. Comparisons made between four different 

 lamps showed concordant results, their values being also 

 in accord with the one-candle pentane standard. Prof. 

 Emerson Reynolds's experiment, illustrating •' The effect 

 on the acetylene flame of varying proportions of carbon 

 dioxide in the gas," was of considerable interest. The experi- 

 ment had arisen from a chance observation by Mr. Goodwin 

 that expired air when mixed with acetylene appeared to increase 

 the luminosity of the acetylene flame, and also to decrease the 

 tendency to deposit carbon in the burners. More careful study 

 had shown that 5-8 per cent, of carbon dioxide in the gas 

 decreased the smokiness of the flame, and especially prevented 

 the clogging of the burners. The increase in illuminating power 

 was certainly not marked, but the mixture containing 5 per 

 cent, of carbon dioxide gave as much light as the acetylene 

 itself, and therefore there is a gain to this extent per volume of 

 acetylene burned. The action of the carbon dioxide was 

 regarded as probably due to its exerting some oxidising effect. 



Agricultural chemistry was dealt with in the report of the 

 Committee on the Carbohydrates of Cereal Straws, and by Dr. 

 Luxmoore, who described a scheme of analysis for Dorsetshire 

 soils, which is to be carried out with the view of obtaining a 

 general knowledge of the soils of the county. Dr. Armstrong 

 also contributed a preliminary report of the Committee established 

 last year for the promotion of agriculture. Dr. Gladstone's 

 report on the "Teaching of science in elementary schools" was 

 followed by an interesting discussion, and Dr. Armstrong gave 

 a suggestive account of methods he had adopted for training 

 children in methods of original inquiry under the title of 

 "Juvenile research." Reports were submitted by the several 

 committees of the Section, which will be published in cxtenso in 

 the Transactions of the Association. Amongst these, those on 

 the action of light upon dyed colours, on isomeric naphthalene 

 derivatives, on the wave-length tables of the spectra of the 

 elements, on the bibliography of spectroscopy, and on the 

 electrolytic methods of quantitative analysis were a continuation 

 of previous work. Two new Committees were formed, one to in- 

 vestigate the relation between the absorption spectra and consti- 

 tution of organic substances, and the other on the chemical and 

 bacterial examination of water and sewage, especially in 

 reference to establishing a uniform method for recording results. 

 The sewage problem was also treated of by Dr. Rideal, in a 

 paper on " Standards of purity for sewage effluents." 



Organic chemistry received a fair share of attention, several 

 papers of importance and interest being read. Prof. Noetling, 

 of Mulhausen, described a new series of colours he had obtained 

 from amidated aromatic amidines, the first series of amidine 

 colours prepared. Dr. Laurie and Mr. Strange showed the results 

 they have obtained in studying the cooling curves of fatty acids. 

 The curve, which is very characteristic for pure fatty acids, such 

 as palmitic and stearic, shows a marked change if i per cent, 

 of another fatty acid is present, and when a larger proportion 

 of the second acid is introduced a second latent-heat point is 

 developed, the curve showing a discontinuity below the solidify- 

 ing point of the mixture. The curves given by these mixtures 

 indicate a reproduction of the phenomena observed by Prof. 

 Roberts-Austen in the case of certain alloys. Messrs. Fenton 

 and Jackson showed that the oxidation of polyhydric alcohols 

 in presence of ferrous iron proceeds on analogous lines to that 

 of tartaric acid, " glycerose, the mixture of glyceraldehyde and 

 dihydroxy-acetone being formed from glycerol ; whilst Dr. 

 Morrell and Mr. Crofts recorded a corresponding result on the 

 oxidation of glucose, the alcohol group next to the aldehyde 

 group being oxidised. The contributions in this branch of 

 chemistry are usually too technical to interest many of the 

 followers of the Association, but this year all organic chemists 

 felt a special debt of gratitude to the President of the Section, 

 Prof. Japp, not only for the value of his address to them, but 

 also for the manner in which he had placed the methods and 

 limitations of modern organic chemistry before a far wider field 

 of scientific workers. 



