100 



KNOWLEDGE. 



March, 1913. 



1879 and 1881 as arising in the same way as the cavities in 

 which the sexual organs (antheridia and archegonia) are 

 sunken, namely, by upgrowth of the surrounding tissue of the 

 thallus. In the simplest case (seen in most species of Riccia), 

 the chambers are simply deep vertical canals, believed by 

 Leitgeb to arise as the result of upgrowth of the superficial 

 cells of the thallus as filaments, each filament being in contact 

 with its neighbours at certain points so as to bound these 

 air-canals. In the majority of Marchantiales, however, the 

 chambers become widened out as the thallus grows, and are 

 roofed over, the roofing layer arising, according to Leitgeb, 

 by lateral outgrowth of the uppermost cells of the vertical 

 plates that form the side-walls of the chambers; while in 

 some cases the originally simple chamber is partitioned up by 

 secondary plate-like ingrowths. 



In 1907, Barnes and Land (Bot. Gazette, XLIV.) examined 

 a number of Marchantiales, and claimed that in all cases the 

 chambers arise by splitting between internal cells of the thallus, 

 in exactly the same way as the intercellular air-spaces in 

 the leaves, and so on, of the higher plants. 



Pietsch {Flora, Band 103) has published the results of 

 his careful investigation of the Riccia thallus, the chief 

 species dealt with being R. glauca and R. fluitans. He 

 has followed in detail the segmentation of the initial cells 

 at the growing-point and the origin of the air-chambers, 

 which in R. fluitans are wide and covered by a roofing-layer 

 in which a pore may or may not be present. His descriptions 

 and figures leave little doubt that Barnes and Land are right 

 in their interpretation of the mode of origin of the chambers ; 

 but it may be added that Leitgeb's own figures are, as is usual 

 in his work, extraordinarily accurate considering that he had 

 not the advantages of modern microtome technique at com- 

 mand, and that it was simply in the interpretation of what he 

 saw that he erred in this instance. Indeed, even after the 

 publication of the paper by Barnes and Land, it appeared to 

 the present writer, from examination of slides similar to theirs, 

 that Leitgeb's interpretation might still be the correct one. in 

 the case of Riccia glauca at any rate. However, the 

 elaborate work of Pietsch appears to settle the question 

 definitely. As this author points out, the view put forward by 

 Barnes and Land that each chamber in the Marchantiaceae 

 arises from a single primary cell (" mother-cell ") can hardly 

 be accepted, for according to their description and diagram the 

 vertical septa between neighbouring chambers would be two 

 cells thick, while as a matter of fact these partitions are but 

 one layer in thickness. 



CHEMISTRY. 



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



LUMINESCENCE ANALYSIS .—In Lehmann's 

 fluorescence microscope, which is used with ultra-violet light, 

 there is a special screen to protect the eye from injury. A 

 description of this instrument and of the uses to which it may 

 be put in analysis is given by Dr. O. Wolff in the Chem. Zeit. 

 (1912, XXXVI, 1039). For example, it has been found that 

 the particles in crude potashes that show a red fluorescence 

 consist of potassium sulphide, while the blue fluorescent 

 particles are mainly composed of compounds of organic and 

 mineral matter. 



Again, this instrument shows that the orange fluorescence 

 of mercuric chloride is caused by the presence of particles of 

 mercurous chloride, the fluorescence of which disappears on 

 heating. If mercuric chloride is chemically pure it does not 

 fluoresce, but traces of calomel may be detected by the 

 luminescence test in many of the preparations on the market, 

 although they would escape detection by chemical tests. When 

 pure mercuric chloride is re-sublimed in a tube, the orange 

 fluorescence will appear, showing that traces of calomel are 

 produced in the process. 



In like manner, pure anthracene shows a blue fluorescence, 

 but when impure fluoresces green, owing to the presence of a 

 substance showing a yellow fluorescence. 



FORMATION OF PETROLEUM PRODUCTS.— It is 

 highly probable that a process of filtration through porous 

 media has played a part in the natural fractionation of petro- 

 leum, and this separation was attributed by Day to the differ- 

 ences in the speed of the diffusion of the different constituents 

 through the capillary passages between the granules of porous 

 earths. From the recent experiments of Gurwitsch, however, 

 [Petroleum, 1912, VIII, 65) it appears more likely that the 

 separation is due to the attraction or absorption of the petro- 

 leum compounds by the particles of the porous earth. Thus, 

 when the same oil was filtered through different porous media, 

 the fractionation followed a very different course ; while, on 

 the other hand, filtration of a benzine solution of a petroleum 

 product through a siliceous earth termed floridin gave exactly 

 the same result as when the solution was shaken with the 

 earth, 9-9 per cent, of the constituents being retained in each 

 case. 



The results of treating a white vaseline for four hours at a 

 high temperature with forty per cent, of floridin were very 

 interesting. The original vaseline contained 9-35 per cent, of 

 paraffin wax, and had a viscosity of 6-7 degrees in Engler's 

 apparatus, but after the treatment the paraffin wax had fallen 

 to 6-80 per cent, while the viscosity had risen to 12-6 degrees. 

 It thus appears that, contrary to the generally-accepted view, 

 treatment of petroleum products with adsorbent agents may 

 cause an increase in their viscosity. 



POISONOUS GASES FROM OIL FIELDS— Mr. H. 

 S. Shrewsbury records a case of a man being killed by 

 breathing the gas at the bottom of a pit beneath a derrick at 

 an oil well near Pitch Lake, Trinidad (Analyst, 1912 

 XXXVII, 486). A sample of the gas issuing from the top of 

 the well was found to have the following composition : — 

 Sulphuretted hydrogen, 0-2 ; carbon monoxide, 1 -9 ; unsatur- 

 ated hydrocarbons, 4-4 ; saturated hydrocarbons, 7-8 ; 

 carbon dioxide, 20-9 ; hydrogen, 31-4 ; and nitrogen 33-4 per 

 cent. 



Since 0-1 to 0-15 per cent, of sulphuretted hydrogen is 

 fatal to human life, while 0- 15 percent, of carbon monoxide is 

 dangerous, and 0-4 per cent, of that gas will destroy life in a 

 short time, it will be seen that the gas issuing from the oil 

 well was extremely poisonous, and that even when mixed with 

 about forty-three per cent, of air, as it was at the bottom of 

 the pit, it would kill in a short time. The gas issuing in 

 bubbles from the small channels and pools of water on the 

 Pitch Lake, and that given off by the pitch itself, had the 

 same tarry and sulphuretted odour as the poisonous gas from 

 the oil fields. It is remarkable, however, that small fishes 

 live in the pools, through which this poisonous gas is con- 

 stantly bubbling. 



It is suggested that this emission of poisonous gas from oil 

 fields is probably not an uncommon occurrence, and that now 

 that attention has been called to the danger, suitable precau- 

 tions may be taken to prevent accidents. 



REDUCTION OF METALLIC CHLORIDES BY 

 SODIUM. — A communication by Mr. M. A. Hunter to the 

 Eighth International Congress of Applied Chemistry (1912, 

 Orig. Communications, II, 125) gives an account of the results 

 obtained by reducing certain chlorides with metallic sodium 

 in a steel bomb. The chlorides of titanium and beryllium 

 were rapidly reduced to the metallic form, and beads of the 

 metals were deposited on the walls of the bomb. In the 

 case of titanium, in particular, the metal was pure and could 

 easily be separated. Neodymium chloride also yielded the 

 metal, but in a condition in which it could not readily be 

 separated from the other substances. 



Silicon chloride was also reduced with difficulty to silicon, 

 while compounds of carbon, such as carbon tetrachloride and 

 sulphide, yielded elementary carbon mainly in the amorphous 

 state, though also containing a little graphite and a 

 microscopic amount of colourless crystals agreeing in 

 properties with crystalline carbon. Among the by-products 

 of the reaction were sodium carbide and carbon hexachloride. 



