302 



KNOWLEDGE & SCIENTIFIC NEWS. 



[December, 1905. 



By C. AiN~ 



CHEMICAL. 



MucHi:!.!.. i-!.A. 



IM.C. 



Coffees without Caffeine. 



The alkaloid caffeine, to which tea and coffee owe their 

 stimulating property, crystallises in glistening white needles, 

 which melt at a relatively high temperature, and can be 

 sublimed unchanged. Tea contains some 3 or 4 per cent, of 

 this alkaloid, and coffee about 1' per cent., while it is also 

 present in mate, or Paraguay tea, and guarana, a beverage 

 prepared by the natives of Brazil from the seeds of PauUinia 

 sorbilis. M. G. Hertrand discovered four years ago that a 

 species of coffee, Cotfcii humhlotiaiui. growing in Madagascar, 

 was quite free from caffeine, although containing a bitter 

 principle to which he gave the name cii/aiiutiinc. Since then 

 he has found several other species of the coffee plant to con- 

 tain only a small proportion of caffeine, and quite recently 

 has e.xamined three new species which were absolutelv free 

 from the alkaloid, but contained a bitter substance analogous 

 to that occurring in C. Iiitmhlutiaiia. All of these coffee plants 

 devoid of caffeine grow either in Madagascar or the neigh- 

 bouring islands, and are not found on the African continent. 

 In order to determine whether the soil or climate had any 

 immediate influence upon the development of caffeine, experi- 

 ments were made with the ordinary coffee plant. C. arabica, 

 but the plants grown in Madagascar invariably yielded the 

 normal proportion of alk.aloid. 



The Cultivation of Plants on Radio- 

 Active Soil. 



Some extremely interesting experiments have been made 

 by M. A. v. Poehl to determine the effect of cultivating 

 pharmaceutical plants at Tsarkoie-Selo, near St. Petersburg. 

 where the soil contains argillaceous schists, which, as is well 

 known, are radioactive. The plants were examined after a 

 year, and were found to contain radium, which, however, was 

 only present in the roots and stalks, and never in the flowers. 



The Utilisation of Natural Gas. 



Natural gas is found in constant association with petro- 

 leum, but has hitherto been put to but little use, at all events 

 in Kurope. In Boryslaw. for instance, it is particularly plenti- 

 ful, but is for the most part allowed to escape into tne air, 

 with the exception of the small quantity used for heating the 

 vessels in which the crude petroleum is distilled. In America, 

 however, it is used as the source of a gas black for printing 

 ink, for the illumination of houses, to which it is supplied 

 under a pressure of half an atmosphere, and as fuel for glass- 

 works and other factories which have been built near the 

 sources of supply. In this country the natural gas discovered 

 at Heathfield, in Sussex, is collected atjd used for lighting the 

 bouses. The possibility of many new applications of natural 

 gas is suggested by the fact that Herr NVolski has taken out 

 a patent in Austria for its liquefaction, and that the process 

 has been found a success in the Carpathian oil fields. The 

 liquefied gas begins to distil at about 106" C, and the first 

 fraction consists in the main of the hydrocarbon methane. 

 The vapour tension of the liquid is relatively very small, and 

 the product can therefore be safely kept or transported in 

 ordinary soda-water syphons. It seems likely to have a 

 great future before it for such purposes as lighting isolated 

 houses and driving small gas-engines and motors, whilst being 

 a bye-product of the petroleum industry its cost will be much 

 less than that of ordinary coal gas. 



A New Ferment. 



There are many species of veast, but until recently none 

 was known th.at was capable of'^ resisting a high temperature. 

 Messrs. Johnson and Hare, however, have separated from 

 eucalyptus leaves a new species possessing this characteristic 

 in a high degree, being able to convert sugar into alcohol at a 

 temperature of over 105 F., which would be fatal to ordinary 

 yeasts. At the end of the fermentation the new yeast, to 

 which has been given the name of Saccluircmyi c Ihcrmunliloniim, 

 falls to the bottom of the ves-sel in a compact agglutinated mass. 

 The cells are more oval and rather smaller than those of 

 the more common saccharomyces, and have several other dis- 

 tinguishing features. The use of this ferment has been pro 



tected by 55 patents in different parts of the world, for its great 

 commercial value is due to the fact that by its means fer- 

 mentations can be carried on in tropical countries, where 

 hitherto this was out of the question. A further advantage is 

 that it is possible by simply heating the cultivations to destroy 

 foreign micro-organisms without injuring the yeast. It is so 

 resistant to heat that it can withstand for a short time a tem- 

 perature of 1 700 ]■'. Even after the cells have been killed by 

 being submerged in water at 176' F., the active agent or 

 enzyme they contain is still capable of producing a weak fer- 

 mentation. 



Sympacthetic Inks. 



Sympathetic inks are connnonly regarded as chemical toys, 

 although the fact that several recent patents for such inks 

 have been taken out shows that they have practical uses of 

 commercial value. One of the earliest means of writing in 

 characters that were nearly invisible until warmed was milk, 

 the use of which was recommended by Ovid, whilst Pliny 

 makes mention of various plants whoso juices were suit- 

 able for the same purpose. Numerous references to secret 

 inks occur in media;val writings, but we can only make 

 a guess as to their composition. Brossonius, writing in 

 a medical treatise in the earlier part of the 17th century, de- 

 scribes a " magnetic fluid," prepared from " arscniated liver 

 of sulphur," only visible when looked at " with the eyes of 

 affection." This appears to have been nothing more than a 

 solution of lead acetate, the characters being rendered visible 

 by the action of sulphuretted hydrogen. This lead acetate 

 ink is described by several other early writers, and notably by 

 Otto Tachen (iCrxj), who points out that there is nothing mag- 

 netic or miraculous in its action. It was described as " sym- 

 pathetic ink " by Le Mort, and the name was afterwards ex- 

 tended to all preparations suitable for secret writing. The 

 curious behaviour of salts of cobalt when heated was first de- 

 scribed by Waiz in 1715. and solutions of one or other of these 

 have since formed the basis of many of the so-called sympa- 

 thetic inks. Cobalt chloride, for instance, is pink in tho cry- 

 stalline condition, but when heated loses water and becomes 

 blue. Characters written with a solution of this salt are nearly 

 invisible on white paper, but turn blue with heat, and then 

 gradually absorb moisture from the .lir becoming pink again, 

 and practically disappearing. In the case of some other sub- 

 stances .1 re-agcnt is required to develop the writing. Thus 

 characters written with gall extract turn black on treatment 

 with an iron salt ; gold chloride gives purple writing with 

 tin chloride, and starch gives a blue coloration with iodine. 

 The last-named ink has long been a favourite with sharpers of 

 the racecourse, two of whom were last year convicted of the 

 fraud. A betting paper giving the names of the hor.ses is 

 written in two kinds of ink, one of which speedily fades away, 

 while the other gradually appears. The disappearing ink is 

 often a weak solution of iodine tinged with starch, and the 

 characters written with this soon fade. I'or the invisible 

 writing a favourite ink is a solution of silver nitrate, which 

 darkens imder the influence of light. An ingenious applica- 

 tion of a sympathetic ink, patented by Kromer, insures the 

 detection of any tampering with an envelope. Ihc dry con- 

 stituents of the ink, e.f;., tannin and iron sulphate, are separ- 

 ated by means of the adhesive gum, so that should steam be 

 used to open the envelope they come into contact and leave a 

 stain upon the paper. A sympathetic method might be based 

 upon the fluorescence of quinine salts imder ultra-violet light, 

 or of other compounds when exposed to the rays of radium, &c. 



GEOLOGICAL. 



Hy FiiUAnii A. Mahtin, F.G.S. 



"Wash-Outs" in Coal-Seams. 



The subject of "w.ish outs" occurring in .some of the middle 

 coal-measures of South ^■orkshire has bcc;n dealt with by Mr. 

 I-". F. Middleton, I'.Ci.S., in a paper recently published in the 

 Quarterly Journal of the Geological Society. He is of (ipinioii 

 tfiat they occupy tlic sites of winding streams, which mean- 

 dered through the .illuvial tracts in which the coal-seams were 

 being formed. This would account for breaks in the con- 

 tinuity of the deposition of certain seams, but true wash-outs 



