Apkii., IQi: 



KNOWLEDGE. 



151 



Thaiiinopten's tticiiisavis. Platyccritiiii bifonnc. and a 

 considerable number of orchids. 



A third class of two small trees, Macitraiifia triloba and 

 M. griffitliiiina. whose hollow stems are pierced and tenanted 

 by ants. These trees have persistent stipules which have 

 glands secreting wa.\y granules, these being gathered and used 

 as food by the ants. In return for this food and shelter, the 

 ants protect the trees from the attacks of larvae. 



ALCOHOLIC FKRMKNTATIOX.— Some interesting re- 

 sults have recently been obtained from further work upon the 

 fermentation of sugars by means of yeast. Harden and Norris 

 [Proc. Roy. Soc, B 82) have found that many yeasts that do 

 not ferment the sugar galactose acquire the property of doing 

 so after being cultivated for a time on a medium containing 

 this sugar. They also find that the juice expressed from such 

 a yeast is capable of fermenting galactose, and that the 

 addition of phosphates to the fermentation mixture causes an 

 acceleration of fermentation similar to that observed in 

 mixtures of glucose, fructose, or mannose and yeast juice on 

 the addition of phosphates. In each case, the phosphate is 

 present in the form of an organic compound, from which it is 

 not precipitated by magnesium citrate. Small quantities of 

 soditun arsenite also accelerated fermentation. 



.As to the nature of the compound formed when a phosphate 

 is added to a fermenting mixture of yeast juice and sugar, 

 ditferent workers have held that (1) the compound is a hexose 

 phosphate containing two phosphoric acid residues; (2) it 

 contains only one phosphoric acid residue, since the osazone 

 obtained from it has only one such residue; (3) it is a triose 

 phosphate. In a recent paper dealing with the mechanism of 

 fermentation. Young {Biochein. Zeitschr., 1911) brings 

 forward evidence to show that the compound is a hexose 

 phosphate with two acid residues, this contention being based 

 largely on the composition of the barium salt of the compound 

 and on the behaviour of its osazone. 



Neuberg and Tir {Biochein. Zeitschr., 10111 have greatly 

 extended our knowledge of the action of yeasts upon sub- 

 stances other than sugars. The chief substances which are 

 fermented in this way, with the evolution of carbon dioxide, 

 are the connnon plant acids occurring in fruit juices, also 

 various components or products of the yeast-cell, e.g., fatty 

 acids, glycerine, and lecithin. 



CHEMISTRY. 



By C. .\iNswoRTH Mitchell, B.X. (Oxon.), F.I.C. 



BACTERIAL DECOMPOSITION OF ARSENIC COM- 

 POUNDS. — .\rsenic is usually regarded as a powerful 

 antiseptic agent — so much so that it will preserve organic 

 tissues from undergoing decomposition for many years. 

 Thus, in the case of the arsenic-eaters of Styria the system 

 becomes so saturated with the drug that when the graveyards 

 are opened the bodies of those who had acquired the arsenic 

 habit may be distinguished by their almost perfect state of 

 preservation. There is also evidence to show that arsenic- 

 eaters arc p.irticularly immune from infectious diseases. 



It is, therefore, surprising to find that certain bacteria can 

 not only live in a strong solution of sodium arsenite, but can 

 also effect its oxidation. This remarkable phenomenon 

 has been discovered by .Mr. A. V. Fuller, and its practical 

 in\portance is emphasised in a circular published by the U.S. 

 Department of .Agriculture, Bureau of .-\nimal Industry. 

 (No. 182. November 9th, 1911.) 



It was found that arsenical dipping fluids used for washing 

 sheep showed an apparent loss of ar.senic after standing for 

 some time in the vats. Experiments proved that this was not 

 due to purely chemical reactions, but was caused by a 

 spontaneous oxidation of the sodium arsenite to sodium 

 arsenate, which escaped detection in the method of estimation 

 employed. The oxidation was shown to be brought about by 

 micro-organisms, which have not yet been isolated or identified. 

 So rapidly did it take place under favourable conditions as to 

 temperature, nature of nutrient .substances present, and so on, 

 that in some experiments the arsenic had been almost com- 

 pletely oxidised in the course of a few weeks. Thus, for 



example, a sample of dipping fluid which contained sodium 

 arsenite in a proportion corresponding to 0-236 per cent, of 

 arsenic trioxide was mixed with suitable nutrient media and 

 inoculated w^ith sheep dip in which the oxidising process had 

 begun. The flasks containing the inoculated liquids were kept 

 for a month at the ordinary temperature in the dark, being 

 meanwhile shaken from time to time to promote the oxidation. 

 Flasks containing the same dipping fluid which had been 

 sterilised by heat were also exposed to the same conditions. 

 At the end of the period it was found that the liquid in the 

 control flask contained 0-222 per cent, of arsenic trioxide, 

 whereas in the case of the inoculated samples the proportions 

 ranged from 0-006 to 0- 198 percent. Owing to the varying 

 conditions to which arsenical dips are exposed in practice, it 

 has not been found possible to fix any limit of time during which 

 a wash might be regarded as materially unaltered, and the 

 circular therefore advises that all arsenical sheep dips should 

 be discarded after being exposed for more than a few weeks, 

 unless it is shown by a chemical estimation that they contain 

 their original amount of arsenic trioxide. 



SILOXIDE: A NEW GLASS.— Claim is made by MM. 

 WolfBurckhardt and Borchers, in a recently-published F'rench 

 patent (No. 432,786 of 1911), for a new glass which is 

 prepared by fusing together pure natural silica with oxides of 

 the silicon-carbon group, preferably titanium or zirconium 

 oxides or a mixture of the two. The resulting products are 

 termed " Z-siloxide " or zirconium glass, and '" T-siloxide " or 

 titanium glass, and have many advantages over pure quartz 

 glass, although they do not possess the same beautiful lustre. 

 An experimental investigation of the new glass has been made 

 by Mr. F.Thomas (Chem. Zeit., 1912, XXXVI, 25), who finds 

 that it is much less liable to undergo devitrification, and that 

 it is less affected by the action of alkalies or other chemicals 

 than quartz glass. The strongest zirconium glass was that 

 containing one per cent, of zirconia, while the titanium glasses 

 (containing 0-1 to 2 per cent, of titanium) were inferior to 

 quartz glass in their power of resisting compression, but were 

 still better than the zirconium glasses in resisting the action of 

 heat. The new glass can be worked by the methods in 

 ordinary use in the manufacture of glass. 



AMORPHOUS SILICON.— A black silicon sulphide 

 obtained by fusing together in an electric furnace a mixture of 

 ferro-silicon and sulphur has been described by Dr. L. 

 Cambi (Chem. Zeiitralbl, 1910, II. 1863). When this is 

 hydrolysed it yields a chemically-active product, which has 

 been found (Afti Accatt Lined, Roma, 1911, XX, 440) to 

 consist, in the main, of a variety of amorphous silicon. A 

 fairly pure sample, containing ninety-six per cent, of silicon, 

 had a specific gravity of 2 ■ 08, while the variety of amorphous 

 silicon discovered by Vigouroux has a specific gravity of 2-35. 

 This new form of silicon is a bright reddish -yellow body, which, 

 when heated for an hour at 900*^ C, in the absence of air, is 

 transformed into a heavier brown product, closely resembling 

 V'igouroux's silicon. The impurities in the active amorphous 

 silicon consist of hydrogen and oxygen, which are probably in 

 combination with the silicon. 



PROPERTIES OF PURE VANADIUM.— Pure metallic 

 vanadium has been prepared by Messrs. O. Ruff and W. 

 Martin, and a description of the methods employed and the 

 properties of the product are given in the Zeit. angew. 

 Chem. (1912, XXV., 49). By fusing vanadium trioxide with 

 a mixture of carbon and aluminium in the .alumino-thermal 

 process, a product containing from ninety- five to ninety-nine 

 per cent, of vanadium was obtained. Or vanadium carbide 

 was first prepared by fusing together in carbon crucibles 

 (heated to a temperature of 2800°C.) a mixture of vanadium 

 trioxide and carbon, and then fusing (at 2000°C.) a mixture 

 of this vanadium carbide and vanadium trioxide in an 

 electrically-heated furnace. 



The melting-point of the pure metal was 1715°C., and its 

 specific gravity at IS-y^C. was 5-688. In the fused condition 

 it w-ould dissolve either vanadium trioxide or carbide, to form 

 mixtures of higher melting-points than the metal. 



