2 10 



NATURE 



[July 2, 1903 



on the mass of the c.c. of water and on thermometer 

 scales. 



Section ii. received some important communications on 

 the auto-puritication of waters. G. Weigelt (Berlin) has 

 experimented on the rates of diffusion of refuse waters 

 into river courses when introduced in different circum- 

 stances ; tests based upon average contamination are quite 

 misleading when injury to the fish is concerned. River 

 water can, owing to its contents in carbonates, bind 

 enormous quantities of sulphuric acid and also of alkalis, by 

 decomposition of the bicarbonates, and iron salts are quickly 

 deposited. F. Fischer (Gottingen) spoke on technically 

 pure water, and regretted that biological tests seemed to 

 supplant chemical analysis ; the methods of sample taking 

 were faulty. In section viii. Vandevelde (Gand) remarked 

 thai rest, absence of antiseptic and chemical compounds, 

 presence of living organisms, and aeration favoured the 

 auto-purification of water courses. Hygiene and navi- 

 gation were in opposition ; in flat country districts rivers 

 should be doubled, a canal to serve for navigation, and the 

 old bed for purification. Ch. Dreyfuss spoke on the septic 

 tanks of Manchester, Proskauer and Erlwein on the ozone- 

 sterilisation plants of Siemens and Halske at Wiesbaden 

 and Paderborn. On the suggestion of Klaudy (Vienna) it 

 was resolved to bring the water question before the next 

 congress. 



G. Lunge reviewed the state of the sulphuric acid manu- 

 facture in a very able paper, recommending water-sprays 

 (not vapour) for the lead chambers, and reaction plate 

 towers with artificial draught, and pointing to the great 

 improvements lately effected in concentration apparatus. 

 Kestner (Lille) described his lead ventilators for artificial 

 draught. E. Hart (Easton, Pa.) reported on sulphuric acid 

 in the United States since 1900, and D. Pennock (Syracuse, 

 N.Y.) on the progress in the soda industry in the United 

 States. G. Beilby (Glasgow) reviewed the position of the 

 cyanide industry, pointing out that the actual plants could 

 supply more than twice as much cyanide as is wanted. 

 Synthetic cyanide processes were further discussed, in 

 different sections, by F. Rossler, G. Erlwein, and A. Frank. 

 The latter two spoke particularly on the Caro-Frank pro- 

 cess taken up by Siemens and Halske. The carbides of 

 barium and calcium bind nitrogen when powdered and 

 heated, forming CaCN,, which, on extraction with water, 

 yields (CN.NH2)2, and on fusion with salt (soda was used 

 for the barium compound which was first prepared) sodium 

 cyanide. The calcium cyanamide can also directly be pre- 

 pared in the electric furnace from lime, coal, and atmo- 

 spheric nitrogen. Decomposed with water vapour under 

 pressure ammonia results ; the calcium cyanamide also gives 

 off ammonia in the soil, and is used as manure under the 

 name of Kalkstickstoif. J. Bueb (Dessau) explained the 

 recovery of the cyanogen from illuminating gas. 



F. Mylius (Reichsanstalt) showed that the loss of weight 

 which glass undergoes when treated with water would 

 afford a basis for the classification of chemical glasses ; an 

 electric conductivity test practically gives the necessary 

 data. R. Dralle described glass blowing machines ; 

 Heinecke, recent improvements in keramics effected at the 

 Royal Porcelain Manufactory of Berlin ; Vogt (Sevres) and 

 Heintze (Meissen) also contributed communications on 

 their porcelains. H. Heraeus, of Hanau, showed his new 

 resistance furnaces, in which platinum foil o 007mm. in 

 thickness is used instead of wire. The new iridium furnace, 

 also shown, is an iridium tube 03mm. in thickness, which 

 was directly heated by continuous currents up to 2000° C. 

 With the aid of these furnaces and the experienced glass- 

 blowers of Siebert and Kiihn, of Cassel, quartz vessels are 

 now made in Hanau. Ordinary quartz crucibles cost about 

 half as much as platinum crucibles; they are attacked by 

 metallic oxides and are permeable to hydrogen above 

 1300° C. (1100° G. according to Hahn), but do not crack 

 on . sudden cooling; water gas converts the quartz into 

 tridymite. Siebert and .KUhn had quartz thermometers on 

 view.. W... Hempel (Dresden) constructs simple high 

 temperature furnaces by cementing small carbon rods to 

 a zig-zag surrounding the crucible ; the shell is iron lined 

 with kieselguhr and carbon. Using an arc furnace and 

 placing the substance in the cup of a hollow carbon rod, 

 he has determined the following melting points : — mag- 

 nesia, 2250° ; lime, 1900° ; alumina, 2068° ; magnesite. 



2000°; porcelain (Berlin) softens at 1550°; Meissen porce- 

 lain at 1850°. In these experiments a rod rests loosely on 

 the substance, and breaks a contact when sinking. The 

 temperature is determined with a Holborn-Kurlbaum optical 

 pyrometer, or a Bunsen photometer of Hempel's, in which 

 the rays are several times reflected ; for this reason 

 Hempel himself regards all these preliminary values as 

 probably too low. H. Bunte (Karlsruhe) demonstrated 

 with the aid of laboratory mantles that neither pure thoria 

 nor pure ceria yield the high luminescence which we obtain 

 by mixtures, and that very small percentages of uranium, 

 platinum, &c., in thoria also produce brilliant lamps, but 

 that none of these are durable. The luminosity is probably 

 simply physical, but there may be catalysis. 



Section iiia., metallurgy, discussed papers by H. Wedding 

 and Th. Fischer on metallic hydrides, by C. Schiffner (Frei- 

 berg) and A. Lodin (Paris) on pyritic smelting, by Ch. E. 

 Munroe (Washington) on mining, metallurgy, and ex- 

 plosives in the United States, Gin (Paris), on extraction of 

 copper pyrites with SO,, &c. In section iiib. Brunswig, 

 Bichel, Blochmann, Mettegang, Eschweiler, Watteyne, 

 O. Guttmann (London), Knight (Krijmel), Lenze, Berg- 

 mann and others had long discussions on the Trauzl lead 

 block test, determination of explosive velocities, transport 

 of compressed gases and liquids, protection of explosive 

 works against lightning, danger from perchlorates in 

 powder, &c. O. Guttmann 's proposal for an international 

 committee on explosion tests in experimental mine galleries 

 did not find sufficient support. 



Section iva. had many good papers by C. Engler, Bergner 

 (Baku), Aisinmann ( Campina), E. O'Neill (California), 

 Harperath (Argentina) on petroleum ; Charitchkow 

 (Grossny) proposed to fractionate technically naphtha in the 

 cold by means of alcohol mixtures. Connstein (Berlin) 

 described the successful splitting-up of fats by the enzymes 

 contained in Rhicinus seeds, &c. ; Lewkowitch (London) 

 referred to the same subject. Other papers were on 

 cyanogen, illuminating and water gas (Bunte and 

 F Fischer), saccharin (Fahlberg), &c. 



Sections iv6., dyes; v., sugar; vi., fermentation and 

 starch; vii., agricultural chemistry; viii., hygiene, pharma- 

 ceutical and medicinal chemistry, and foods; xi., legal and 

 economical questions, were all very busy. 



Section ix., photochemistry, discussed papers by J. M. 

 Eder (Vienna) and Ollendorf (Berlin) on sensitometers ; 

 on latent images, by J. Waterhouse (Eltham) and Schaum 

 (Marburg) ; on colour photography by additive synthesis, 

 by A. Miethe and R. Neuhaus (Berlin) ; on photochemistry 

 in the United States, the centrifugal bromide of silver, and 

 other points, by L. Baekeland, Yonkers, N.Y. ; on the reso- 

 lution of the finest spectrum lines on Doppler's principle, 

 by O. Lummer ; and an exhaustive study of the dichroic 

 fog, by A. Seyewitz (Lyon). 



In section x., electrochemistry and physical chemistry, 

 J. Traube and G. Teichner (Berlin) performed an experiment 

 apparently disproving Andrews's views on the critical state 

 of gases. A glass tube is partly filled with carbon tetra- 

 chloride ; it contains also little spherical floats of glass 

 of different densities. The tube is jacketed with paraffin 

 and diphenylamine. When heated to and above the critical 

 point, the meniscus disappears, and the floats do not all 

 collect in the middle portion of the tube. This is to prove 

 that there is no uniform density in the vapour. Repeating 

 experiments of de Heen and Dwelshauvers-Dery, Traube 

 considers that van der Waals's molecular gas volume con- 

 stant h is not constant, but increases when the liquid 

 passes into the gaseous state, and that the vapour contains 

 liquidogenous and gasogenous molecules the proportions of 

 which depend upon the temperature. At the critical 

 temperature both molecules are soluble in one another in 

 any proportions. 



W. Nernst (Gottingen) showed an apparatus with the 

 aid of which he has determined the vapOur densities of CO3 

 with o-30i7mg., of NaCl with o i6mg., of S with o-57mg. 

 of substance. The substance is brought in an iridium 

 vessel, which is lowered into a tubular iridium furnace 

 of Heraeus and heated up to 1950° C. The weighing is 

 done on a balance, consisting of a capillary glass tube as 

 beam, bent down at the end to serve as pointer, and resting 

 on a quartz thread ; this balance weighs to oooimg., and 

 j can be loaded with 2mg. maximum. The values found 



NO. 1757, VOL. 68] 



