gyratory movement of the chamber's contents, due t o external cooling, and descend steadily downward along the walls. An instance is cited from the observations made at Wasquetal upon the temperatures a t three different points in the first chamber of a plant. Under similar conditions of external temperature, with the same pyrites, t h e same ovens, and the same towers, the temperatures observed a t the three points in a rectangular chamber were 9 0 ° , 8 8 O , and 86' C. In the chamber with curved top, which replaced the former, they were 7 5 " , 7 j o ,and 74' C. The more rapid cooling and the close approach to uniformity are noteworthy. The director of the works a t Kratzwieck is, however, of the opinion t h a t a more gently curved roof is quite as effective as one of semicircular shape and more desirable from several standpoints. In the plant now under construction he plans to modify this feature. At the outset i t must be noted t h a t the cost o f construction, per unit of cubic chamber space, is higher than b y the old method. At Kratzwieck the additional cost was found to be about 33 per cent. 'l'his figure would vary according t o local factors. 'There seems t o be no doubt of the manifest economy in space, frequently a n important factor where chemical works are hampered in their development b y lack of. sufficient available area for building. At Kratzwieck the two units already built on the Moritz system occupy b u t two-thirds of the area formerly covered b y three separate units before the fire. Yet these two units produce more sulphuric acid than the three units t h a t were destroyed. The next important economy is in the amount of nitric acid required t o produce the maximum effect in t h e lead chambers. The newly erected plant of the "Union" yields daily about 7 kilograms of acid (50" Baume) per cubic meter of chamber space. Formerly, a t this rate of production, 0.7-0.8 kilogram of nitric acid (36' Baumi.) was consumed for each I O O kilograms of chamber acid of t h e above strength. This consumption has now fallen to very nearly 0.5 kilogram. I t is t o be noted t h a t 0.9 kilogram is ;L very common figure in German acid works. I n 1900 the average consumption was 1.4 kilograms in American acid works burning pyrites. This loss of nitric acid is an important item in the cost of producing sulphuric acid. I n Germany i t constitutes 4-8 per cent. o f the total cost. I t is obvious t h a t a saving ( ~ If or 2 per cent. in this direction constitutes a notablr csconomy. The inventor guarantees a maximum loss o f 0 . 6 kilogram where chambers are producing 7 kilograms daily per cubic meter. I t may be mentioned in this connectiqn t h a t in the " Union" system water in the form of spray is admitted to.the chambers in summer and in t h e form of steam during the winter. Apart from the direct saving on the daily cost of production, the director of t h e "Union" works is confident from his study of the plant during the few months t h a t i t has been in operation t h a t there will be ultimately a very material saving in the item of depreciation, through the prolonged life o f the chambers, and the ease and simplicity with which any necessary eventual repairs can be executed.
A MODIFICATION OF THE FRARY ELECTRODYNAMIC STIRRING DEVICE. B y J. hf. KNOTEAND W. R. WORK.
Received March 14. 1912.
The use of a solenoid for the rapid determination ot' metals in the electrolytic way was proposed by Frary (Jozrrizul o j tht, A m e r i c a n (-'hemica1 Society, Ko'vember, 1907, and in other publications). He employed the usual form of solenoid which is a coil of copper nire cylindrical in shape and hollow, and enclosed in an iron case. The beaker containing the electrolyte is put into the hollow space in the center of the coil and :i current passed through the electrolyte in the usual way. At the same time a current through the solenoid produces a magnetic field in the region of the beaker which in conjunction with the electrolyzing current causes a rapid circulation in the electrolyte. The disadvantages of this form of apparatus are that the electrolyte is not in sight and an inspection of the electrodes during the process of electrolysis is not easy. The solution becomes quite hot and in some common determinations this is not desirable. The use of a rooling coil complicates the apparatus. .
MODIFICATION
By actual tneasurements the magnrtic field pro ducecl b y a solenoid was shown t o be practically as strong at the top of the coil as i t is at any point in the interior, and an inch above the top it still amounts to 40 per cent. of this strength, gradually decreasinn as the distance increases. a s shown by Fig. T . The lines I
o f force which constitute the field pass without hin-
drance through glass, paper, wood, brass, etc., so it is a simple matter t o put the coil of the solenoid around an iron core, cover the top with a suitable material and place the beaker containing the electrolyte on it. By using electrodes with bent stems a very simple
J u l y , 1912
%’HE JOLJRAITAIA01; /~‘ViU~JSTRIRT2 AiVD E N G I N E E R I N G C H E M I S T R Y .
and convenient electrode holder can be used in conjunction with this form. Both electrodes are fastened t o a small block mTliich is raised with one harid while the wash bottle is used with the other. The objection might be raised t o our modification t.hat on account of the strong field a t the bottom of the beaker and the m-cbak one a t the top, most of thc stirring would be at the bottom. I t is true t h a t the vigorous stirring does originate at the bottom, but on account of the free circulation, the upper p a r t of the solution gets all the stirring necessary. I n any event the solenoid stirring does not produce the commotion in the solution caused by a mechanical stirrelbut nevertheless results can be obtained quickly. T h ? avcra,ce strength nf the magnetic field nicasiircrl i n the rcyion o f the beaker is i o 0 gausscs. RESULTS.
f>tar!- has describer1 in detail the speed and acc.urnc>.obtained hy the use o f a solenoid in electrolytic Tvnrk. ) ‘l‘hc. f n u r scilviioids shoivn in Fig. 2 have becn in usc i n t.hc Chemical Dcpartmrnt ( i f the Pittsburg Tcstiti: (
Laborator\- for several months and are vcr\- satisfactory for the large variety of determinations we arc called upon to make. TT’e recognize the) merits oE the various forms o f apparatus proposed for mechanical stirring b u t prefer our present equipment. K e find it much more satisfactory than the stationar!. gauze electrode alone where a variety of determinations arc to be made. With stationarJ- gauze c%lectrodesin 1 2 5 cc. of solution containing about one gram of copper we allowed three amperes t o pass for fifty minutes in order to be sure all the copper had been deposited. With thc solenoid the same amount of copper is deposited in thirty minutes under the same conditions using t h e same electrodes. With a higher current the results can be obtained in less timr. TESTING I,ARnR.\TnR\-, CARNEGIE TECHNICAL ScHnnLs.
PITTSBURGH
____.
THE
UNDERWRITERS’ LABORATORIES APPARATUS.
EXTRACTION
B y HENRY.I. CARY-CURR.
Received April 16, 1912
It has been found necessary in certain lines of cxtraction work t o devise f o r routine work a method t h a t is both rapid and convenient, such, for example,
53s
as t h e determination o f certain cxtractable constituents of rubber insulation on mire, ctc. I n such a case the moisture content (generally less than onehalf of I per cent.) is a negligible factor in the determination and may therefore be overlooked except in special cases where it is especially desired. Based on this ground t h e Chemical Department of the Underwriters’ Laboratories a t Chicago have spent several >-earsin developing methods and apparatus to be used in a standard procedure for chemical tests of rubber compounds used on wires and cords. Any form of extraction apparatus may be uscd, b u t i t must conform to the following spccificatinns: ( I ) “ The extraction cup shall be surrounded by thc vapor of the solvent a t its boiling point.” ( 2 ) “ T h r condensed solvent shall fall directly on thc sample.” (3) “ T h e outlet from thc extraction cup shall br a t the bottom only.” (4) “ Kn rubber or cnrk stoppers shall cotne in contact with thc solvent.” (5) “Samplt shall bc p u t directly into extraction. cui) without thc use OE a paper thimble--a disc o f filter paper or its equivalent a t the bottom o f thc cup bc-ing depcrirlc~l upon to hold hack thc sc~liclp a r t of thc. s:implc.” F ~ ~ l l c i m i tthc i ~ inanipula t i o i i i elf t l i c ;ihove-illc-ii tioncci mc-thocls i t f)rcrinics neccssul-!. t o r s t r a c t , i t i t r i ;I tarccl flask \rhich rnust h~ r c w c i ~ h c r l: r i i i l Lvhich n ~ u s t thcrcfot-e hc. o f proportions xnd st!-lc suitahlc lor ariinissicin to t h c s hoivs ant1 1)aiis ( i f a i l i i r c l i n a r ~;~i n a l ~ ~ t i c : ~ l halancr. liapiclit!. ani1 ct7icif,ni,!- 01’ c o i i ( 1 u i s a t i o i i tiigct hci. I\ i t h (’as? o f i~ianipulatioii; i i i i l i n ~ t a l l ai tc i r i \\,ell ; I < simplicit!. i~l‘c~onstructionanti thcrciorc’ Ii)\v c,rist 01 tnaintenanccx rinli rcplacemtTnt\ \ w e other points t ( Jhc. ronsiderctl. To meet thcse requirements R t i r \ v apparat 11s h a s ceptional merit I t consists of a short, metallic, spiral-titbc reflux condenser, whose, inlet and outlet tubes project through metal platc n hich scrx c\ the double purpose o f a support for the condenser and a closure for the extraction flask The flask is of rather conical form with rt long neck and flat bottom Two holes arc horecl on opposite sidei ot t h e upper rim of a 1)oixclain Gnoch cruciblc i\ hich is suspended from t hc condenser by passing through the holes a short piece o f platinum 01 aluminum TT ire whichalso passes through the loop a t the bottom of the condenser. The charge having been placed in the crucible, t h e condenser and crucible are placed in the neck of the flask, the water connections made and when a good flow of water has been c~
