January, 1913. 



KNOWLEDGE. 



21 



which it acts ; and there are various facts in favour of this 

 view — the lines of deep colour that occur along the veins of 

 many flowers, the frequency with which the walls of cells 

 appear to contain oxydase, the occurrence of oxydase in the 

 mesophyll cells adjoining the bundle sheath, and the evidence 

 provided by the mutual influence of stock and scion in grafted 

 plants and in graft-hybrids. 



Again, it has been found that the nature and amount of 

 oxydase contained in a plant tissue varies in an orderly 

 manner according to external conditions. Among the con- 

 ditions which determine this fluctuation are light and darkness. 

 Plants subjected to normal illumination possess less oxydase 

 than those kept in darkness ; after one or two days of exposure 

 to darkness, plants of P. sinensis contain more peroxydase 

 than sister plants kept under normal conditions of 

 illumination. 



Should the results of similar investigations with other plants 

 show that this diurnal variation of the oxydase content of plant 

 tissues is general, we may perhaps discover therein the means 

 whereby many of the phenomena of periodicity shown by 

 plants are maintained and regulated. The light and darkness 

 of day and night set up rhythms in the plant ; the leaves of 

 various plants assume nocturnal and diurnal positions, and the 

 rhythm thus established may be maintained for a certain time 

 under uniform conditions of illumination, as in the Sensitive 

 Plant and many others. Animals also show a similar 

 periodicity ; the shrimp-like Hippolyte varians rolls up its 

 brilliant pigment-bodies (chromatophores) at night and becomes 

 sky-blue in colour ; but when daylight comes the pigment of 

 the chromatophores is spread out in superficial networks. 

 Kept in darkness these animals retain for many days this 

 periodic habit, and when the hour of night arrives, though they 

 have no light to tell it by, they lay aside their daily garb and 

 put on the uniform of night. So also the " plant-animal " 

 Convoluta roscoffensis, which lives on the seashore, orders 

 its behaviour by the sun and moon, lying on the sand till the 

 waves of the rising tide are upon it and then descending to 

 security and darkness ; when the tide recedes it rises to the 

 light. Even the uncongenial surroundings of a tea-cup and a 

 laboratory fail to break this habit ; for in these surroundings 

 its uprisings and down-lyings keep time with the tides. It is 

 possible that light and darkness may work these wonders of 

 periodicity and rhythm through the control of chemical agents 

 such as oxydases. 



CHEMISTRY. 



By C. Ainsworth Mitchell, P. A. (Oxon.), F.I.C. 



THE HARDENING OF FATS.— For many years one of 

 the chief problems of the oil industry has been to obtain a 

 harder material from soft fats, and numerous ingenious 

 methods have been tried, though only with limited success. 

 The chemical problem involved in the ideal process is the 

 addition of hydrogen to unsaturated fatty acids or their 

 glycerides as represented, for example, in the case of oleic 

 acid by the equation : — 



ClH Hfl4 O't "I - H2 = ClH Hjtfi O2 



oleic acid stearic acid 



Oleic acid is the chief constituent in most oils, while stearic 

 acid is a main constituent of solid fats such as lard and tallow. 



All attempts to make the hydrogen combine with the 

 unsaturated compounds in this way proved failures until a 

 few years ago it was discovered by MM. Sabatier and 

 Senderens that the combination could be effected by bringing 

 the hydrogen and the liquid fat together at a high temperature 

 in the presence of finely-divided nickel, which acted as a 

 catalytic agent. 



This discovery was followed by other processes in which 

 other metals or metallic oxides such as cobalt, palladium and 

 platinum were used as the catalytic substances, and numerous 

 patents on these lines have been taken out for the manufac- 

 ture of solid fats suitable for food and candle-making from 

 liquid and semi-solid fats. 



In the current issue of the Chem. Rev. Fett Ind.. (1912, 

 XIX, 247) there is a description by Dr. A. Bomer, of the 



chemical and physical properties of a number of these 

 hardened fats prepared from earthnut oil, whale oil and 

 cotton seed oil. In each case solid products resembling lard 

 or tallow, according to the duration of the process, were 

 obtained. From whale oil, for example, a hard white tallow- 

 like fat melting at 45 • 1° C. was prepared, while earthnut oil 

 gave a product which closely resembled lard both in its 

 appearance, chemical properties, taste and smell. 



As these hardened fats are now being sold as food products 

 physiological tests were made to discover whether any 

 injurious substances were formed in the process, but they 

 were found to be quite innocuous, provided that care had 

 been taken to eliminate all traces of the nickel used in the 

 manufacturing process. Stress is laid upon the point, how- 

 ever, that only liquid fats that are already fit for human food 

 should be used as the raw material, while such fats as 

 horse-fat, bone fat, whale oil and the like should be kept for 

 technical purposes such as the making of soaps and candles. 



METROPOLITAN WATER BOARD'S REPORT.— The 

 sixth annual report of the results of the chemical and 

 bacteriological examination of the London waters, which has 

 just been published, contains many details of great interest, 

 to which here it is only possible to allude briefly. The raw 

 waters, from which the supply is drawn, consist principally of 

 rivers that have previously been polluted with sewage, and in 

 the future it will be an increasingly difficult matter to obtain 

 sufficiently satisfactory water to meet the greater demands 

 upon the waterworks. Obviously, the greater the quantity of 

 the water drawn from a river the more impure will be that 

 which remains. Chemical purification of sewage effluents 

 has rendered them much less objectionable ; but apart from 

 sterilisation there is no practical method of removing bacteria 

 from these effluents. 



Fortunately, the effect of mere storage of the water is 

 automatically to reduce the number of bacteria to the extent 

 of over ninety-nine per cent., so that on subsequent filtration 

 of the water a reasonably safe filtrate is obtained. For 

 example, the average number of microbes in raw Thames 

 water during the twelve months ending March, 1912, was 

 9155 per cubic centimetre, while after subsidence and filtration 

 of the water there were only 17-2 per cubic centimetre. 

 •In Dr. Houston's opinion it is hardly conceivable that 

 any pathogenic micro-organism would succeed in reaching 

 the filter beds after a sufficient period of storage. At the same 

 time he lays stress upon the importance of obtaining water 

 in as pure a condition as is practically possible, notwithstand- 

 ing the proved safeguard afforded by efficient storage. 

 Theoretically it should be possible to bring all river water to 

 the same degree of purity before its intake into the water- 

 works and its delivery to the filter beds; but in practice during 

 periods of flood it is necessary either to draw upon such water, 

 which is unsuitable for the purpose, or to deplete the reservoirs 

 by closing the intakes and thus reduce the period of storage 

 for water subsequently taken into store. 



For these reasons Dr. Houston advocates the desirability 

 of taking greater supplies of water at favourable periods than 

 is at present permitted. Apart from this, it is suggested that 

 supplementary processes of purification might with advantage 

 be employed occasionally, in addition to the present processes 

 of devitalisation of bacteria by sedimentation and removal of 

 the bulk of the remainder by filtration. 



CHEMISTRY AT THE BRITISH ASSOCIATION.— 

 The address of Professor Senier, President of the Chemical 

 Section at the Meeting of the British Association in Dundee, 

 is an interesting outline, full of suggestion, of what chemistry 

 is and by what methods it works. It is clearly demonstrated 

 that imagination is necessary for the advance of the science, 

 and that our educational resources should be devoted to 

 assisting promising students in the direction of research rather 

 than to giving an elementary smattering of indigestible facts 

 to everyone. 



Of the papers of more general, apart from purely chemical 

 interest, mention may be made of The Report of the Com- 

 mittee on the Study of Plant Enzymes particularly with 



