JCNE 8, 1883.] 



SCIENCE. 



519 



any other body ; 2. The absorption increases as the 

 difference of temperature between the radiating and 

 . absorbing plates decreases ; 3. The absorption is 

 probably complete when both plates are at the same 

 temperature. Magnus' exceptions were probably not 

 due to impurities, but to a difference of temperature 

 of the two plates. — (Ann. phys. chem., xix. 1.) 

 C. B. P. L1017 



Electricity. 

 Hall effect. — Dr. E. H. Hall finds that the values 

 of the ' rotational coefficients ' given by him at the 

 Tork meeting of the British association for zinc, 

 aluminum, copper, brass, and lead, are confirmed by 

 later experiments. On trying the effect of change 

 of temperature, only a negative result was obtained 

 with gold; with iron, the increase was two-thirds of 

 one per cent, with a rise of 1° C. The coefficient, 

 with change in the strength of the field from 1,000 

 to 7,500 absolute units, seemed to increase ; but, of 

 this, Dr. Hall does not feel sufficient confidence to 

 publish his results. The object of another experi- 

 ment was to determine whetlier any part of the rota- 

 tional effect could be made permanent. For this 

 purpose, a thin piece of very hard steel spring was 

 used as the plate. The direction of the equipotential 

 lines was permanently changed by the action of the 

 magnet. This change was in the same direction as 

 the temporary effect due to the magnet's action, 

 and perhaps equal to two per cent of this. — {Amer. 

 joufn. sc, XXV. 21.5. ) [1018 



ENGINEERING. 



The poTwer of a steamship. — The Oregon, of 

 the Guion line, is to be the most powerful and the 

 fastest of the transatlantic passenger-steamers. Her 

 displacement is about 11,000 tons. Her engines have 

 three cylinders, and are of 13,000-horse power. The 

 boilers contain 74 furnaces, consume about 300 tons 

 of coal per day, evaporate 2,700 tons of water, require 

 6,000 tons of air to support the combustion, or a 

 volume of nearly 175.000,000 cubic feet, and the 

 power developed is sufficient to raise about 200,000 

 tons one foot high per minute. The ship will make 

 20 iiautidal miles (knots) per hour, against an esti- 

 mated resistance of 94 tons, or twenty times the re- 

 sistance overcome by the most powerful locomotive. 

 The Atlantic will be crossed in six days in good 

 weather. — (Lond. engineer, April.) K. H. T. [1019 



The exhaust-steam injector. — Mr. L. J. Groves 

 read a paper before the Institution of engineers and 

 shipbuilders in Scotland, March 20, describing the 

 exhaust-steam injector. It resembles the feed-water 

 injector of Henri Giffard both in principle and- in 

 its general construction. It forces the feed-water 

 into the boiler by the action of the e.xhaust-steani at 

 nearly atmosplieric pressure, at the same time heat- 

 ing considerably the water passing through the 

 instrument. It differs from the usual forms of Gif- 

 fard injector in having the 'mixing' or 'combining' 

 nozzle split in such a manner that it lies open when 

 the apparatus is not working, but closes up to form 

 the standard form of nozzle when the instrument 

 starts into operation. The steam-nozzle is much 

 larger than that of the common instrument, and has 

 a central spindle, of cone shape, to direct and con- 

 centrate the jet. The instrument starts automati- 

 cally when the engine starts. It draws cold water, 

 and forces it into a high-pressure boiler at a tempera- 

 ture of 190° F. (88° 0.). On a locomotive it has 

 forced feed-water into the boiler at a temperature of 

 277° F. (136° C), against a steam pressure of ten 

 atmospheres. — {Trans, inst. eng. shipb. Scotland, 

 April.) K. H. X. [1020 



CHEMISTRY. 

 (Organic.) 

 Action of hydrochloric acid on caffeine. — 



When caffeine is heated with fuming hydrochloric 

 acid to 260° in a closed tube, E. Schmidt finds that 

 it is completely decomposed: — 



CaHi„N40j+ 6H20 = 

 2CO2 + 2ISrH2CH3 + NH3 + CH2O2 + CsHjNO,. 

 Caffeine prepared from theobromine proved to be 

 identical in its chemical and physical properties with 

 the natural base. The decomposition of theobro- 

 mine, when heated with hydrochloric acid, is shown 

 by Schmidt and Pressler to be represented by the 

 equation, — 



CjHsNiO, + 6H.0 = 

 2 CO J + NH.CH3 + 2NH3 + c'sHjNOj + CHjO.. 



By oxidation with nitric acid, theobromine gave 

 methylparabanic acid and methylamine, and caffeine 

 gave dimethylparabanic acid and methylamine. In 

 the preparation of theobromine from cacao, Schmidt 

 found in the mother-liquors needle-sliaped crystals 

 which proved to be caffeine. The action of hydro- 

 chloric acid upon xanthine is shown by the equa- 

 tion, — 



CbHjNjO, + 6H2O =2C0, + 3NH3 + CnHsNOj + CH.Oj. 

 — (^)m. cAeni., ccxvii. 270.) c. F. M. [1021 



Relative reactive po-wer of the halogens in 

 mixed haloid ethers. — L. Henry observed that in 

 chlorbromethylen (CHjOlCHzBr) the bromine atom 

 was removed by potassic hydrate, sodic ethylate, 

 potassic phenolate, potassic acetate, and potassic 

 sulphocyanate. Argentic nitrate substituted the 

 group NO:j for the bromine atom, and a bromnitrate 



of silver (AgjiiQ j was precipitated in quantity 



corresponding to the amount of argentic nitrate 

 taken. The author regards this fact as evidence of 



Ag-NOs 

 the formula I for the nitrate. When the 



Ag-NO;, 

 latter reaction was tried on cliloriodethylen, iod- 

 nitrate of silver was precipitated. By the action of 

 nitric acid, the iodine atom was replaced by the group 

 NO;j. In bromiodethyleu, the iodine atom seemed 

 to be much less reactive than in the presence of 

 chlorine; and, in general, the difference in reactive 

 power between chlorine and bromine was much 

 greater than between bromine and iodine. — ( Comptes 

 rendus, xcvi. 1062, 1149.) c. r. M. [1022 



METALLURGY. 



A nevsr .refining process. — At a recent meeting 

 of tlie Societe de 1' Industrie minerale, M. Thiollier 

 communicated the details of a method of refining 

 pig, and finished iron and steel, by the action of damp 

 hydrogen. To assure himself that the well-known 

 laboratory experiment may be carried out on a large 

 scale, he has erected experimental works near Paris, 

 liaving four furnaces with cast-iron retorts capable of 

 treating about one ton at a time. The retorts are 

 coated inside and out with a vitriflable substance to 

 prevent oxidation, and loss of gas through the pores 

 of the metal. Hydrogen is introduced tlirough small 

 metal tubes; and, in order to prevent all danger of 

 explosion, the air in the retort is displaced by carbonic- 

 acid gas before the hydrogen is allowed to enter. 

 After being annealed for a few hours in an atmosphere 

 of hydrogen at a dark-red to clierry-red heat, malle- 

 able cast iron acquires all the properties of steel. 

 Coarse steels may be changed into fine tool steel. On 

 wrought iron the action is slower. The cost is esti- 



