9 2 



SCIENCE- G OSSIP. 



CHEMISTRY 



CONDUCTED BY C. AINSWORTH MITCHELL, 

 B.A.OXON., F.I.C., F.C.S. 



Limits of Sense of Smell. — An ingenious 

 apparatus has been devised by M. Berthelot for 

 the purpose of measuring the limits of the sense 

 of smell. It consists of a series of large flasks in 

 which air saturated with a given odoriferous com- 

 pound may be successively diluted until the odour 

 is no longer perceptible. For example, in one 

 experiment the atmosphere in the first flask, when 

 saturated with iodoform vapour, contained IT 

 milligramme in four litres of air. On transferring 

 40 c.c. of this air to the second flask the odour was 

 still strong, but after two more such dilutions it 

 was no longer possible to distinguish the odour in 

 the air of the fourth flask. In the case of musk, 

 however, the scent was still perceptible after a 

 dilution 1,000 times greater than this. 



Action of Ether on Plants. — It appears 

 from the interesting experiments of J. Fischer that 

 in many cases ether has a stimulating effect upon 

 plants during the latter part of the resting period. 

 Tulips, after being etherised, bloom from eight to 

 twelve days earlier than those untreated, though 

 the bloom is less lasting. On the other hand, if 

 bulbs be treated with ether before the formation 

 of their roots their growth is less rapid. Shrubs 

 may be forced into bloom from three to four 

 weeks earlier than those grown in the ordinary 

 way. In the case of the lilac, however, the colour 

 is fainter than usual, though exposure of the plant 

 to a temperature of 50-54° F. after the treatment 

 with ether improves both the colour and size of 

 the flowers. The beech is retarded by ether. 



Arsenic in Malt Kilns.— Since our last note, 

 on this subject {ante, vol. vii. p. 369) a consider- 

 able amount of investigation has been made as to 

 the best means of preventing the deposition of 

 arsenic on malt. The most recent communication 

 is that of Mr. T. Fairley, F.I.C., Public Analyst for 

 Leeds, who has made experiments to determine 

 whether the use of fuel free from arsenic would be 

 an absolute safeguard in cases where impure coal 

 had been used for a long period. He has found 

 that the floor of the malting kiln and the walls 

 above act as condensing surfaces for the arsenious 

 vapours, and that when these surfaces become 

 overcharged it is futile to employ pure fuel so long 

 as the products of its combustion pass over this 

 arsenic on their way to the malt. The amount of 

 arsenic in the dust adhering to the tiles and wall 

 was enormous, ranging from 0'25 to 1 per cent, on 

 the tiles, and from 0-0025 to 0-06 per cent, on the 

 walls. Mr. Fairley concludes that it is impossible 

 to bestow too much care on the cleansing of the 

 dust from the malt kilns. It is not safe to trust to 

 any mechanical screening or brushing of the malt. 



Theory of the Incandescent Mantle. — 

 The use of incandescent gas-mantles has greatly 

 increased during the last few years, and they are 



now the chief method of illuminating in Germany. 

 They are prepared by dipping an elastic cotton 

 " stocking" into a solution of salts of certain "rare 

 earths," drying it on a conical wooden mould and 

 eventually igniting it until only a completely white 

 skeleton remains. In the process of ignition the 

 mantle contracts to about a third of its original 

 size. According to Bunte an average mantle yields 

 at first a light equal to 61 candles, but after 300 

 hours its luminosity falls to 52J candles. Compared 

 with the mantles of 1895 those manufactured at 

 the present day consume less gas and give a more 

 constant light. The nature of the light depends far 

 more upon the composition of the mantle than on 

 the quality of the gas, as is shown by the following 

 examples : — 



White Orange yd] Green 



Light Light 



Zirconia . . 40 . . 27 . . 30 . . — 

 Lanthaiia . . 40 . . 40 . . 40 . . 20 

 Thoria ..20 .. 30 .. 28 .. 50 

 Didymia .. — .. 3 .. — .. — 



Ceria ..— .. — .. 2 .. — 



Erbia .. — .. — .. — .. 30 



The intensity of the light emitted by a mixture of 

 thoria and ceria reaches its maximum when the 

 proportion of the latter is - 9 per cent. By measure- 

 ment of the radiations it has been found that' 

 this mixture of thoria and ceria, when heated in a 

 Bunsen flame, reaches a temperature about 300° C. 

 higher than a substance like iron oxide under the 

 same conditions. When the thoria is heated alone, 

 the radiations in the red, green, and blue parts of 

 the spectrum are approximately equal, whilst with 

 ceria alone there is a decrease in the radiations 

 from the red to the blue. Yet in the above mixture 

 there is a great increase in the radiations on pass- 

 ing from red to blue. E. Bauer accounts for this 

 by the assumption that the optimum proportion of 

 ceria is in a state of " solid solution," as it were ; 

 whilst any ceria above that amount is in a sort of 

 suspension or mechanical admixture, and on being 

 heated will emit ultra-red rays, like any other 

 foreign substance, and tend to prevent the mantle 

 acquiring the high temperature which it needs for 

 the emission of its full quantity of light. 



Action of Alcohol on the Gastric Juice. — 

 Kecent experiments on dogs by A. Frouin and 

 M. Molinier, the results of which are published in 

 the " Comptes Rendus," show that alcohol, whether 

 taken with the food or injected, promotes the 

 secretion of the gastric juice. This action is to be 

 attributed to the stimulation of the whole nervous 

 system, and not merely to local action. 



A Standard for Milk. — On August 1st new 

 regulations on the subject of milk come into force. 

 Hitherto milk which is abnormal in composition 

 has often been successfully defended on the plea 

 that the natural product of individual cows can 

 vary within wide limits. And although in certain 

 cases the Bench has held that feeding the cow on 

 improper food, so that it produces an abnormal 

 secretion, constitutes an adulteration, this view has 

 not been generally accepted. In future all milk 

 containing less than 3 per cent, of milk fat and 8 - 5 

 per cent, of non-fatty solids is to be presumed to be 

 not genuine, and the onus of proving the contrary 

 is to rest with the vendor. The milk of Dutch 

 cows is noted for being abnormal at certain seasons 

 of the year ; but this appears to be mainly due to 

 the cattle being left in the fields until too late in 

 the season, for soon after stalling the milk gradually 

 reassumes its ordinary composition. 



