VOL. XXIII. No. 3.] 



POPULAE SCIENCE NEWS. 



37 



Practical Cljenjistry aijd tlje ^rts. 



AN IMMENSE DYNAMO. 



The large dynamo machine represented in 

 the engraving, is in operation at Neuhausen 

 Switzerland, where it is used to produce the 

 current for an electric furnace, for the reduc- 

 tion of aluminium from its ores by the Her- 

 oult process, which is very similar to that in- 

 vented some years ago in this country by 

 Messrs. Cowles and Maberry. In the Cowles 

 process the intense heat generated by a current 

 of large quantity, reduces the aluminium di- 

 rectly, while the inventor of the Ileroult pro- 

 cess claims that in his furnace the chemical, or 

 electrolytic power of the current is utilized, as 

 well as its heating qualities, although this is 

 still an unsettled point. 



Two of these dynamos are in use, and are 

 operated by water power, from the river 

 Rhine near by. The framework carrying the 

 inducing magnets is cast in two solid pieces 

 and weighs 20,000 pounds. Unlike most dy- 

 namo machines they arc not self-exciting, but 

 the exciting current is obtained from a sepa- 

 rate machine, which produces a current of 

 three hundred amperes with an electromotive 

 force of sixty-five volts. The large dynamos 

 develop a current of sixteen volts only, but, 

 as it is one of six thousand amperes, it is well 



calculated to produce in the electric furnace 

 the intense heat necessary to tear apart the 

 atoms of that most refractory element alumin- 

 ium, from the oxygen or other elements with 

 which it is combined. The exceedingly low 

 tension of the current produced by these enor- 

 mous dynamos will be better appreciated 

 when we state that its electro motive force is 

 only about equal to that produced by ten or- 

 dinary Leclanche cells, such as are used for 

 the telephone, or to ring electric bells. The 

 quantity of this low-tension current, how- 

 ever, as represented by the number of amperes, 

 is many thousand times greater, and produces 

 the powerful metallurgical effects referred to 

 above. 



The capacity of the Neuhausen works at 



present is about six thousand pounds of ten 

 per cent, aluminium bronze daily, equal to the 

 reduction of six hundred pounds of pure 

 aluminium. Neither the Cowles nor the He- 

 roult process have yet been found applicable 

 to the economical production of pure alumi- 

 nium unalloyed with other metals, but we 

 have little doubt that this application will be 

 made in the future, and the ■ use of the metal 

 greatly increased. 



PHOTOGRAPHS OF ELECTRIC 



SPARKS. 

 The accompanying engraving is a fac- 

 simile of two photographs of the sparks or 

 discharges from a Holtz electrical machine, 

 and therefore represent electricity at a very 

 high tension. They were taken by a French- 

 man, M. Charles Mussette, in the ordinary 



way by exposing a sensitive plate placed in a 

 camera, to the action of the spark as it passed 

 between the poles of the machine in a dark 

 room. The subdivision of the discharges is 

 rather remarkable, and their resemblance to 

 the forrrjs of a flash of lightning very striking. 

 This would naturally be expected however, 

 for, as far as we know, the only difference 

 between the discharge of a Holtz machine 

 and that of a thunder cloud is one of magni- 

 tude. When we remember that in such a dis- 

 charge the eye only perceives a single line of 

 light, the superior power of the photographic 

 plate for the observance of scientific phenom- 

 ena is very manifest. Photography is becom- 

 ing more of an aid to scientific investigation 

 every day, and it is hard to say when it will 

 reach its full development. 



Another scientist, M. Ducretet, has ob- 

 tained similar photographs without using a 

 camera at all. He simply places the sensitive 

 plate between the poles of the machine in a 

 dark room, and allows the spark to pass over 

 the plate itself, thus impressing its form di- 

 rectly upon it. Very beautiful and interesting 

 pictures are said to be obtained by this 

 method. 



The original article and engravings of M. 

 Mussette are published in Xa Aature, from 

 which we copy them. 



LABORATORY NOTES. 



A New akd Curious Alloy is produced 

 by placing in a clean crucible an ounce of cop- 

 per and an ounce of antimony, and fusing 

 them by a strong heat. The compound will 

 be hard, and of a beautiful violet hue. This 

 alloy has not yet been applied to any useful 

 purpose, but its excellent qualities, independ- 

 ent of its color, entitle it to consideration. 



Incineration of Coke and Graphite. 

 — Stolba recommends the addition of silver 

 powder, prepared by the reduction of silver 

 chloride in the moist way. Finely ground 

 graphite or coke is mixed with an equal 

 weight of pulverulent silver and heated to 

 redness in a platinum crucible. Fusion of 

 the silver must be avoided to prevent the de- 

 struction of the crucible. 



On the Purification of Mercury. — 

 J. M. Crafts finds that mercury may be puri- 

 fied in large masses by the simple aspiration 

 of air through it. He places the merciuy in 

 a glass tube 5 cm. in diameter and i .5 m. long, 

 lying on an inclined wooden support. The 

 lower end is closed by a cork through which 

 pass a funnel tube for the introduction of the 

 mercury, and a stop-cock for its removal. 

 The other end is put in communication with 

 a water exhaust pimip, and in forty-eight 

 hours all the impurities will be found as a co- 

 herent powder in the upper end of the tube, 

 and the mercury can be drawn oft' practically 

 pure. This powder is too voluminous in the 

 case of mercury that has been used to amal- 

 gamate zinc to permit the process to be at 

 once used for such metal. Zinc and lead 

 were introduced into mercury, and, after puri- 

 fication by a current of air, it left no residue 

 when distilled in a vacuum. 



«»► 



[Original in The Popular Science Newn.] 

 SOME OF THE CONSTITUENTS OF DRINK- 

 ING WATER AND THEIR MEANING. 



BY 



PROFS. PETER T. AUSTEN, PH. D., F. C. S. , 



AND 



FRANCIS A. VVILBER, M. S. 

 PART I. 



The analytical determinations usually made in 

 a drinking water are as follows : — Suspended Mat- 

 ter, Total Solids, Chlorides, Free Ammonia, Albu- 

 minoid Ammonia, Nitrates, Nitrites, Oxygen re- 

 quired to oxidize Organic Matter, and Dissolved 

 Gases. We shall explain briefly the more common 

 meanings of these determinations. 



SUSPENDED matter. 



The turbidity of water is owing, as a rule, to the 

 presence of fine particles of solid matters in sus- 

 pension, that is, not dissolved, but swimming about 

 in it. This suspended matter consists of clay, 

 mud, finely comminuted parts of leaves or other de- 

 bris, or indeed, of ground up remains of any sub- 

 stances which are insoluble in the water and which, 

 by any means, may be carried into it. Often these 

 particles are of a remarkable degree of fineness, in 

 which case the water may take several months to 

 settle clear. This suspended matter, as a rule, is 

 not deleterious, except in so far as it makes the wa- 

 ter oftensive to the sense of sight. What influence 



