F u s in g m e ta ls , o re s, a n d th e lik e , a n d c o m p o s itio n s th e re fo r. C. Mil n e s and G. A. Qu a y le
(B.P. 477,107, 26.9.36).—Addition of Y, Ba, Nd, Pr, and V to a Thermit charge covering a loosely packed m aterial, e.g., Fe, in a destructible (Al) container enables the tem p, given by th e Therm it to be con
trolled. F. M. L.
T r e a tm e n t of e x tru d e d m e ta ls [lead]. St a n d ar d Tele ph o n e s & Ca b l e s, Lt d., Assees. of A. J . N.
Duclos(B.P. 477,813,11.6.37. U .S ., 7.11.36. Addn.
to B.P. 433,553; B., 1936, 956).—In the extrusion of P b cable sheaths, the die has passages term inating in outlet ports to direct steam over the surface of the product, the ports being autom atically and selectively closed when the tube is forced off-centre by non-
uniform cooling. F . M. L.
M a n u fa c tu re of le a d allo y s [for ca b le s h e a th s ].
Goodlass Wall & Lea d In d u s t r ie s, Lt d., and B.
Jones (B.P. 479,215, 8.10.36).—The alloys contain Te 0-001—0-25 and Cu 0-03—1% ; they retain then- fine-grained structure even after fusion-welding.
F . M. L.
S o ld e rin g c o m p o s itio n s [flux es]. J . Ba r n et t
(B.P. 476,697, 19.6.36 and 4.5.37).—Finely-divided flux, e.g., N H 4C1, ZnCl2, is dispersed in rosin and the m olten m ixture filled into hollow tubes of solder.
F . M. L.
(A) S in te re d h a r d m e ta l a llo y s. (B) M a n u fa c tu re of s h a p e d b o d ie s of h a r d m a te r ia l. P.
M a r t h (B.P. 478,025—6, 30.11.36).—(a) Claim is made for sintered alloys of a lower carbide of W, Mo, Ti, V, Zr, Ce, Si, B, Al, Be, or Cr, w ith a binder metal, e.g., W 2C 65, Co 35%. (b) The alloys are heated in a mould until the binder m etal melts.
F . M. L.
S in te re d h a r d m e ta l a llo y s. F. Kr u p p A.-G.
(B.P. 478,534, 2.11.36. Ger., 2.12.35. Addn. to B .P. 465,323; B., 1937, 934).—The V4C3 m ay be replaced by V boride and/or nitride, and/or the TiC by nitride; e.g., an alloy of WC w ith Co 5-5, TiC 10, T i nitride 4, and V nitride 1-5% is claimed.
L. C. M.
M a n u fa c tu re of s in te r e d h a r d m e ta llic allo y s.
W. H. Hatfield and H . Burden (B.P. 477,181, 2.9.36).—Powder m ixtures of W, Ta, Ti, Mo, Cr, or V carbide w ith Fe, Co, or N i are briquetted and the product is sintered a t 1400—1700° and rapidly cooled in an inert atm . in a H 20-cooled chamber.
F . M. L.
P r e p a r a tio n of m o u ld e d a r tic le s of a h a r d a n d d ifficu ltly fu sib le allo y . Fedam Soc. A n o n . (B.P. 477,572, 1.2.37. Switz., 31.1.36).—A powder m ixture of carbides of Ti, Zr, Ce, Th, Cr, Mo, W , U, 80—95, Sn- or Ba-bronze (Cu -4C 50%) 0-1—5, and Fe, Co, or Ni > 15% is heated in a C mould in an inert atm . until the bronze m elts; the mass is finally compressed while cooling. F. M. L.
P r o d u c tio n of m e ta llic tita n iu m . D e u t s . Gold- U. SlLBER-SCHEIDEANSTALT VORM. ROESSLER (B.P.
479,014, 8.9.37. Ger., 10.9.36).—TiCl4 vapour is bubbled through fused KC1 covered with alkali m e ta l; th e process is carried out in H 2 a t 700—900°.
F . M. L.
P u rific a tio n of im p u r e n o b le m e ta ls [silv e r].
Distillers Co., Lt d., and H . Langw ell (B.P.
477,522, 26.6.36).—Finely-divided Ag is heated a t 400° for 2 hr. to allow th e im purities to diffuse to the surface of the particles and there oxidise so th a t they can be subsequently dissolved by treatm ent with an appropriate solvent which does n o t attack
the Ag. F. M. L.
R eco v e ry of p re c io u s -m e ta l v a lu e s f r o m o re s . Me rrill Co., L. D . Mil l s, T. B. Cro w e, and J . C.
Ha u n (B.P. 477,099, 23.7.36).—Pregnant solution from the cyanide-leaching of Ag and Au ores is deaerated by vac. treatm ent followed by addition of N a2S20 4, and is treated w ith Zn to p pt. Ag and A u ; the p pt. is separated from th e solution by flotation with CuS04 and a xanthate. F. M. L.
P ro d u c tio n of m e ta llic s u rfa c e la y e r s . W. C.
He r a e u s Ge s. m.b.H . (B.P. 478,916, 26.2.37. Ger., 10.12.36).—R h strip is electrically h ea ted a t 1800°/
0-001 m m . an d th e resu lting vapour condensed on articles, e.g., mirrors and op tical m easuring in stru m en ts, placed in th e v ic in ity , th e surface being
finally polished. F . M. L.
(A) C a stin g , a n d (B) p u rific a tio n , of m a g n e s iu m . (a) F . H a n s g ir g , (b) G. S c h i o h t e l , Assrs. to A m er. M a g n esiu m M e t a l s C orp. (U.S.P. 2,066,564 and 2,066,579, 5.1.37. A p p l., [a] 21.11.34, [b]
13.1.34. A ustr., [a] 25.4.34, [b] 30.3.33).—(a) 2—
10% of Sb2Ss, Sb2S3, or B i2S3 is mixed w ith the mould m aterial for casting Mg. (b) C and Fe are removed from Mg by melting th e m etal under a m ixture of FeCl3 30, ZnCl2 30, MgCl2 30, and MgF„
10%. A. R . P.
M a g n e s iu m -b a s e a llo y s. Hig h Du t y Al l o y s, Lt d., an d W . E . Prytherch (B .P . 477,721, 16.10.
and 31.12.36).—A lloys con taining A l 2— 12 (4), Sn 4 —12 (6), A g 0-5—12 (1), M n > 2 (0-2)%, and one or m ore o f th e m etals Zn (1), Sb (0-3), A s, B i, Cd an d/or P b > 3 % o f each, are h ea ted a t 450° for 20 hr., quenched, an d reheated a t 130—350° (250°) for 15 hr.
F . M. L.
[F u sed s a lt b a t h fo r] h e a t- tr e a tm e n t of lig h t- m e ta l a llo y s c o n ta in in g m a g n e s iu m . I. G.
Fa r b e n in d. A.-G. (B.P. 477,836, 1.7.36. Ger., 28.8.35. Addn. to B.P. 448,944; B., 1937, 53).—The bath consists of m ixtures of alkaU chromates and dichromates such th a t the [Cr20 7"] : [Cr04"] ratio is
< th e equilibrium val. a t the operating tem p, of the bath. A suitable m ixture is composed of N a2Cr20 7 30, K ,Cr20 7 10, N a2C r04 3 pts., a n d K 2C r04 1 pt. and is worked a t 35 0-575°. F . M. L.
P r e p a r a tio n of a h im in iu m g r a n u le s . G .Be n d a- Lutz We r k e Ge s.m.b.H . (B .P . 477,756, 6.7.37.
Austr., 5.8.36).—Al foil is fed into a beating mill and there to m to flakes, the pieces so formed being shaped into granules by the rotating hammers. F . M. L.
M e ta llic [a lu m in iu m ] p ig m e n t p a s t e s . Metals Disin teg rating Co., In c. (B.P. 477,451, 30.6.36.
Ger., 16.5.36).—Al is ground in a ball mill with a thinner, e.g., Vamolene, and a leafing agent, e.g., stearic acid; the product is filtered off to give a re
latively dry cake, and this is mixed with more thinner and leafing agent for storing. F . M. L.
Cl. X .—METALS ; METALLURGY, INCLUDING ELECTROMETALLURGY. 539 A lu m in iu m allo y . ,T . E. Br a d b u r y (B.P.
476,930, 16.6.36).—The alloy contains Cu 1-1—
5-5 (2-7), Zn 1—6-8 (6-2), Mg 1-6—5 (2-2), Ee 0-02—
3 (0-2), Si 0-05—1 (0-2)%, and optionally > 4 % (in all) of N i >3-5, Mn 2, Sb 3, Co 2-5, or Ti 1%, and
> 2 % (in all) of Cr, Ag, Mo, Be, Pb, W, V, B, Zr,
Ce, Th, and Li. E. M. L.
A lu m in iu m allo y . H . C. Hall, and Rolls -Royce, Lt d. (B.P. 477,278, 20.6.36. Addn. to B.P.
350,110; B., 1931, 764).—The alloys contain Ee 1-5—3 (1-7), Mg 0-7—1-74 (1-5), Cu 2-5—6 (5-2), Ni
<0-2, Si 1-3 (0-65), B 1 (0-6), and Mn and a t least one of the m etals Cr, Co, Mo, W, Y, 0-2—2% (in all).
F . M. L.
A lu m in iu m a llo y s. Ve r e in. De u t s. Metall- w e r k eA.-G. (B.P. 478,659, 22.7.36. Ger., 24.1.36).
— M achinable, corrosion-resistant alloys containing Mg 0-3—3 (1), Cu 0-1—6 (4—5), Si 0 -4 ^ 1 (0-6), Mn 0-4— 1-5, P b (part or all of which m ay bo replaced by one or more of the metals As, Sb, Bi, Cd, or Sn 0-01—
1) 0-1—3 (1-5), Fe 0-4—5 (0-5), and Zn 0-1— 12 (0-3), with or w ithout Ni or Co 0-1—3 and/or Cr 0-1— 1%,
are claimed. L. C. M.
A lu m in iu m -b a s e a llo y s . Br it. Al u m in iu mCo., Lt d., and J . H. Dickin (B.P. 478,125, 8.7.36).—
Claim is made for A l alloys containing Cu >12, Mg
>0-5, Sn > 2, and Sb 0-1—5%. The Sb is added as a hardener alloy prepared by prolonged heating of
Sb with A l a t 920°. F . M. L.
T h e r m a l tr e a tm e n t of lig h t m e ta ls a n d lig h t- m e ta l a llo y s. K . Bo n a t h and C. Al br ec h t, Assrs. to De u t s. Go ld- u. Sil b e r-Sc h e id e a n st. vorm. Ro essler (U.S.P. 2,066,454, 5.1.37. A ppl., 31.10.35. Ger., 31.10.34).—A salt bath for annealing Al and its alloys consists of KC1 25— 45, NaCl 15—25, CaCl2 10—50, BaCl2 10—20, SrCl2 5—20, and BaC 03 1—25%, the BaCOs being added to provide a pro
tective alkalinity. A. R. P.
R e m o v a l of sca le -lik e d e p o s its fr o m v e sse ls m a d e of a lu m in iu m o r a lu m in iu m allo y s. M.
La n d a u e r and K . Lochmuller (B.P. 478,209, 13.7.36. Ger., 25.7.35).—The surface is cleaned with a pasty m ixture of kieselguhr or clay, urea, (NH4)2S 0 4, an oxidising agent, e.g., (NH4)2S20 8, a polyhydric alcohol, e.g., glycerol, and H 2S 0 4. F. M. L.
C o lo u rin g of m e ta l s u rfa c e s . W . K . Wil so n, F . M. Thomas, and De Havilland Aircraft Co., Lt d. (B.P. 477,286, 20.6.36).—Duralumin air-screws are polished, degreased, burnished with 40-mesh Fe shot, and anodically oxidised; the oxide film is finally immersed for 15 min. a t 80—90° in 0-5% aq.
Nigrosine-black containing 0-1% of AcO H , to produce
a m a tt black finish. F. M. L.
E le c tr ic m u ffle fu rn a c e s p a r tic u la r ly fo r b ra z in g to o l tip s to to o l s h a n k s . Fir t h- Ster ling Stee l Co., Assees. of E. B . Welch (B .P . 479,344, 28.7.36. U.S., 22.6.36).—The furnace comprises a muffle lining of heat-resisting m etal closed a t one end by a plate carrying a tube for introduction of inert gas and disposed in a chamber containing heating elements so arranged as to localise the heat around the junction of the shank and tip of the tool.
F. M. L.
PP (B.)
[F e rro u s m e ta l] w e ld in g e le c tro d e s. T. C. R.
Sh e p h e r d, and Metropolitan- Vickers Electrical
Co., Lt d. (B.P. 479,376, 19.10.36).—The core is first spirally wound with insulated F e ware or tape and then coated with a flux containing TiO,, clay, S i02, felspar, and Fe-Mn, -T i, -Mo, or -V to give the necessary weld m e ta l; e.g., for welding Cu-bearing steels the flux contains ilmenite 32, T i0 2 24, felspar 5-5, clay 10-5, Fe-M n 12 pts., bonded with Na2S i03
and starch. F. M. L.
N ick el an o d e s. Mo n d Nick el Co., Lt d. (B.P.
479,004, 14.7.37).—Im proved N i anodes contain C 0-05—2%, Mg, Ti, and Si 0-05— 1% of each, Co
>0-5% , and Fe, Cu, and Mn >0-25% of each. A preferred alloy for a cast anode contains C 1, Mg 0-28, Ti 0-25, Si 0-53, Co 0-35, Fe 0-14, Cu 0-1, and Mn 0-12%, and for a rolled anode C 0-3, Mg 0-31, Ti 0-25, Si 0-53, Co 0-35, Fe 0-14, Cu 0-08, and Mn 0-12%.
F. M. L.
E le c tro ly tic re fin in g of c h r o m iu m a n d fe rro - c b r o m iu m a n d p ro d u c tio n of c h ro m ic a c id . E . Liebr eich (B.P. 477,381, 23.3.36. Ger., 21.3.35).—
C r03 is produced, with or without deposition of Cr, by electrolysis (impure Cr anode) of a solution containing H 2S 04 and a (K, a Na, or an NH4) chromate in such a way th a t the charge on the cation is > th a t on the
S 04". F. M. L.
E le c tro ly tic p ro d u c tio n of m a g n e s iu m . Mag n e siu m Metal & Al lo y s, Lt d. (B .P . 478,276,17.7.36.
Ger., 20.7.35).—A molten m ixture o f alkali chlorides with < 3 0 (< 2 0 )% of MgCl2 is circulated through a series of cells in such a way th a t the level in each is kept const. The spent electrolyte is enriched in MgCl2 and recirculated after removal of impurities
(MgO) by settling. F . M. L.
(A) A p p a ra tu s fo r e le c tro p la tin g m e ta llic a rtic le s . (B) M e a n s fo r co n veying m e ta llic a r tic le s th ro u g h a p p a r a tu s fo r e le c tro p la tin g . Br ig h tside Plating Co., Lt d., and J . Kr o n sb e in (B .P . 477,094 and 477,905, 9.7.36).—The articles are (a) carried through th e bath on a rotating disc which can be moved laterally so as to adjust the working con
ditions; (b) suspended from a carrier bar which is moved by a conveyor system and alternately lowered and raised to bring the articles into and out of a sequence of tanks, e.g., cleaner, wash, acid-etching,
and plating tanks. F . M. L.
C h ro m iu m -p la tin g of a lu m in iu m a n d a lu m in iu m a llo y s. Dr. Fin c k h Ge s.m.b.H . (B .P . 476,720, 1.4.37. Ger., 7.4.36).—The articles are first thinly coated with F e by pickling a t 92—95° in a b ath con
taining FeCl3 and HCl, and th en plated first w ith 0-02—0-036 mm. of N i and/or Cu and finally with
0-01—0-2 mm. of Cr. F . M. L.
B a th fo r an o d ic t r e a tm e n t of a lu m in iu m . R . W. Buzzard (U.S.P. 2,066,327, 5.1.37. Appl., 28.5.34).—The bath contains C r03 5 and Cr(OAc)3 5— 11 w t.-% ; the articles are treated therein a t 30—40 v. for 30—60 min. a t 30—40°. A. R. P.
G o ld -p la tin g c h ro m iu m -a llo y s te e l a r tic le s , s u c h a s p e n n ib s . A. H . St e v e n s. From C.
Howard Hu n t Pe n Co. (B .P . 478,444, 21.8.36).—
Prior to Au-plating (with or without an interm ediate
540 B R IT IS H CHEMICAL AND PHYSIOLOGICAL ABSTRACTS.—B.
deposit of R h or P t), the oxide film is removed from the Cr-steel surface hy cathodic etching in dil. HCI.
L. C. M.
E le c tro d e p o s itio n of ta n ta lu m a n d t a n ta lu m a llo y s. H . H . Ar m st r o n g and A . B. Me n e f e e
(B.P. 477,519, 24.6.36. U.S., 24.6.35).—The electro
lyte contains a double fluoride of T a and an alkali m etal together with tartaric acid and, if alloys are desired, NiCl2 and/or a W fluoride. F . M . L.
E le c tro d e p o s itio n of tu n g s te n a n d it s allo y s.
H . H . Ar m s t r o n g and A. B. Me n e f e e (B.P. 478,640, 18.5.36. U.S., 18.5.35).—An electrolyte of aq.
N aH F 2 (pH 4) is employed, w ith an anode of com
pressed discrete W, W alloy, and/or WC or alloying m etal carbide; alternatively, a perforated container packed with such a compressed m ixture m ay be used.
L. C. M.
T e s tin g tb e th ic k n e s s of m e ta l c o a tin g s . W . M. Bu r d e n and S. G. Cl a r k e (B .P . 476,876, 13.6.36).—The thickness is measured by the tim e taken for a je t of corroding liquid, a t const, head, impinging on the surface to penetrate the coating. A suitable solution for Cu or Ni coatings is FeCl3 150, CuS04,5H20 100, and AcOH 200 g./l., and for Cd or Zn coatings N H 4N 0 3 17-5 g. and n-HCI 17-5 c.c./l. F . M. L.
M e th o d of a n d fu rn a c e fo r [in te rn a l] c o a tin g of [steel] p ip e s w ith m e ta l [c o p p er]. M . Br a u n
(B .P . 478,938, 4.6.37. Ger., 18.6. and 21.7.36).
H g b o ile r. F u rn a c e fo r e n a m e lle d F e . O re - re d u c in g m a c h in e s .—See I. E n a m e llin g ta n k s e tc . C e ra m ic b o d y -m e ta l jo in ts .—See V III.
[C a stin g ] a c c u m u la to r p la te s . E le c tric a l con
ta c t.—See X I.
X L —ELECTROTECHNICS.
M o d e m e le c tric fu rn a c e s fo r th e a h u n in iu m a n d lig h t m e ta l in d u s tr ie s . G. C. Ca s t l e (Metal
lurgia, 1938, 17, 191— 192).—Types of furnaces used and their advantages ape summarised. S. J . K.
L o w -freq u en cy in d u c tio n m e ltin g fu rn a c e s fo r lig h t m e ta ls . F. Es s m a n n (Metallwirts., 1938, 17, 234—236).—The characteristics of this typo of furnace are described, and operating costs given for a typical furnace used for melting Al alloys.
C. E. H.
E le c tr ic a l p r o p e r tie s of s o lid s . I I . S y s te m p o ly v in y l c h lo rid e -tric re s y l [trito ly l] p h o s p h a te . I I I . T h e r m a l b re a k d o w n of p la s tic is e d p o ly v in y l c h lo rid e . R . M. F u o ss (J. Amer. Chem. Soc., 1938, 60, 451—456, 456—460; cf. A., 1937,1, 582).—
I I . The conductance of the plastic [containing 40%
of^(€SGH 4Me)3P 0 4] is composed of (a) an electrolytic conductance and (b) a pure a.-c. response which is practically independent of frequency over the range (15 — 3) X 10° cycles; (a) varies exponentially with reciprocal te m p .; (6) varies little w ith temp.
The e is approx. a linear function of log frequency over a fairly wide frequency range, and a t > 6 0 cycles increases w ith rising tem p.
I I I . The variation of conductance w ith voltage has been determined for the plastic, and the results are discussed theoretically. The resistance decreases approx. as a linear function of the square of the applied
voltage. The max. voltage Vn a t which a steady state is possible, with a const, surfaco temp. T 0, is given by Vj? = 8ap0T 02/p, where a is the therm al conductivity, p0 th e sp. resistivity a t T 0, and [5 a measure of the ra te of change of p w ith T . At voltages > this crit. val. electrical failure occurs, and a t lower voltages therm al failure m ay occur.
E . S. H.
I n d u s tr ia l p o s s ib ilitie s of e le c tro -o rg a n ic r e d u c tio n . S . Sw a n n, jun. (Ind. Eng. Chem., 1937, 29, 1339—1341).—A review. H . A. P.
(A ) M o s t s u ita b le d ia p h r a g m s a n d w o rk in g c o n d itio n s fo r e le c tro d ia ly s is . (B ) P u rific a tio n of n ic k e l h y d ro x id e b y e le c tro d ia ly s is , (c) P u r i fic a tio n of n ic k e l h y d ro x id e p re c ip ita te b y e le c tro filtra tio n . S. Ok a (J. Soc. Chem. Ind.
Japan, 1937, 40, 393b, 393—394b, 394b).—(a) For the anodic diaphragm of a 3-compartm ent electro
dialysis cell a membrane of am photeric m aterial, e.g., chromated gelatin, is preferred. The optimum current efficiency is attained when the anodic and cathodic diaphragms have large positive and negative charges, respectively. W ith both, the porosity of the membrane, the c.d., and the concn. of the solution in the electrode com partment should be small.
(b) In the electrodialysis of Ni(OH)2 (I) 19 mem branes were tested. The above results were, in general, confirmed. Current eificieney is, however, low, and the purification of m aterials from large am ounts of electrolyte by this m ethod is not practic
able, although the process is suitable for th e removal of traces of im purities left after other treatm ents.
(c) The suspension of (I) is filtered through filter-paper supported on a perforated P b plate, washed, and electrolysed for 10—30 min. (at 8—32 v.), the Pb being the positive and a Cu gauze covered w ith parchm ent paper the negative pole. The m ethod of pptn. of (I) is im portant, and preferably 2N-NaOH- N a2C 03 ( 9 : 1 —3 :1 equivs.) (25 vols.) is added to 2N-NiS04 (22-5 vols.) and the m ixture boiled. The process is more rapid and requires much less H 20
th an washing alone. I. C. R.
T r a n s ie n t v o lta g e s a t th e b e g in n in g of d is c h a rg e of a s to ra g e c e ll a n d t h e i r re la tio n to th e a c tu a l a n d “ tr a n s f e r ” r e s is ta n c e of th e p o sitiv e p la te . T. S. Co l e (Trans. Electrochem. Soc., 1938.
73, P reprint 7, 83— 111).—On open circuit large differences in acid concn. persist from th e centre to the surface of the active positive paste, the corre
sponding potential variations causing an increased rate of current flow from localised and restricted areas when th e cell is initially discharged. An explanation of th e transient voltage-tim e curves, based on the laws of electrical networks, is advanced.
J . W. C.
C o n s titu e n ts of th e L ec lan ch e cell. I I . R o le of s o o t. Z. He r r m a n n [with E. Ha h n] (Monatsh., 1938, 71, 175— 185; cf. B., 1937, 936).—Soot causes an increase in the internal resistance of th e cell. I t m ay be replaced by graphite, provided grinding of the m ixture is sufficient. Soot derived from C2H 2 is b etter th an th a t from rubber, and th e latter is better than active C, as a constituent of the depolarising m ixture. The soot does not act as a carrier of 0 2,
Cl. X I.—ELECTROTECHNICS. 5 4 1
nor is its action entirely one of increasing the porosity of the mixture. Tho soot particles serve to increase the degree of contact between the M n02 and the graphite. Soot particles of m oderate size give the
best results. H . J . E.
A p p lic a tio n s of e le c tric a l p re c ip ita tio n to in d u s tr ia l efflu en t g a s e s . H. J . Bu s h (Inst.
Chem. Eng., Feb. 18, 1938, 10 pp.).—A brief survey is made of the development of the a r t of electrical pptn., and sp. examples are given of the application to cement works, power stations, metallurgical works (either for recovery of valuable fume or cleaning gas for subsequent use), etc. Tho advantages arising from the capacity to remove even the finest dust, the low resistance to the flow of gas through the plant, and the small consumption of electricity are pointed
out. F. J . B .
E le c tr ic a l d u s t p re c ip ita tio n . J . Wu y c k e n s
(M6m. Univ. Bruxelles, 1937, 95 pp.).—Details are given of a laboratory investigation relating to the electrical pptn. of dust from a stream of air. Appar
atus comprising a device for uniform and regular distribution of dust in tho air stream, a small Cottrell typo of precipitator, and an oil filter for removing dust from the effluent stream of air is described.
Amongst factors studied are : effect of dust concn. on the efficiency of pptn. (no change of efficiency was found for concns. up to 5 g./cu.m .); effect of e.m.f.
employed within the range 7300— 12,000 v . ; effect of the velocity of the air stream, and the relation between e.m.f. and current in the discharge. A high degree of purification is more readily obtained by a reduction of velocity of the stream th an by an increase of e.m.f.
The scale effect controlling the possibility of applying laboratory results to large-scale plant is discussed.
J . S. G. T.
S electiv e e le c tro s ta tic s e p a ra tio n . H. B.
Jo h n so n(Min. Tech., 1938,2, Tech. Publ. 877,11 pp.).
—The relative electrostatic conductivity, or suscepti
bility to a static charge or field, of 90 minerals of particle size < 16- and > 150-mesh was investigated.
Tho m ajority of silicates, carbonates, and oxides tested were found to be susceptible to an interchange of the polarity of the electrodes and were designated as electrostatically “ reversible.” All tho native ele
ments, except S, were irreversible. The separation of anthracite from bituminous coal is given as an example of the possibility of selective separation m ethods depending on the property of reversibility.
A. K . G. T.
In s u la tio n re s is ta n c e of c e ra m ic m a te r ia ls a t te m p e r a tu r e s u p to 900°. G. Pf e s t o r f and E. F.
Ric h t e r (Physikal. Z., 1938, 39,141— 150).—Certain ceramic m aterials show a hysteresis loop in the tem p .- resistance curve, which is connected with electro
lytic conduction. The effect of the electrodes on the conduction is examined with electrodes which could provide ions (Ni, P t, Ag) in the m aterial (porcelain) and those which could no t (graphite). Actually Ni and P t did no t provide ions, bu t they were detected with Ag and in this case a loopless curve was obtained.
There is a close connexion between the m igration of alkali ions in porcelain and the existence of the tem p .-
resistanco loops. A. J . M.
R e s u lts , n ew p o s s ib ilitie s , a n d lim its of th e m a g n e tic te s tin g of m a te r ia ls . W. Sc h ir p (Stahl u. Eisen, 1938, 58, 235—240).—Magnetic processes for detecting fundam ental faults in m aterial and also irregularities arising from cold-deformation, non- uniform heat-treatm ent, etc., by d.c. and a.c., with separate and coupled excitation, are described.
D.c. and separate excitation penetrate the m aterial and enable th e deeper-lying faults to be detected, whilst a.c. and coupled excitation are better adapted to the determ ination of surface failures and involve loss costly apparatus. A new instrum ent (described) determines faults in ferrous and non-ferrous tubes and bars by means o f an eddy current.
C. M. A.
E d g e c o rre c tio n i n th e d e te r m in a tio n of d i
e le c tric c o n s ta n t [of s h e e t in s u la tin g m a te r ia ls ] . H. L. Cu r t is and A . H. Scott (P ro c. A m er. S o c.
Tost. Mat., 1936, 36, II, 815—829).—D e te rm in a tio n of ed ge c o r re c tio n in m e a s u r e m e n t of d ie le c tric c o n s ta n t. A . H. Scott (Ibid., 1937, 37, I I , 655—
660).
D e te rm in in g H 20 in g a s e s .—See I. R a d io g ra p h y of co al. E le c tric a l e q u ip m e n t of coke- oven etc. w o rk s .—See II. P u rify in g cellulose a n d its d e riv a tiv e s. Im p re g n a te d p a p e r.—Sep V. B le a c h in g . A p p lic a tio n s of flu o rescen ce.
—See VI. G la ss a n a ly s is . C e ra m ic m a t e r ia l- m e ta l etc. jo in ts . R e fra c to rie s fo r in d u c tio n fu rn a c e s.—See V III. D e te rm in in g m o is tu r e in w o o d .—See IX . D e te rm in in g A120 3 in ste e l, an d V in allo y s te e ls e tc . T e s tin g fa tig u e of ste e l.
R a d io g ra p h y of ste e l. H a rd e n in g h ig h -s p e e d ste e l. N ic k e l-d ip p in g F e . X -R a y d iffra c tio n s tu d y of fa tig u e of m e ta ls . E x a m in in g m e ta l su rfa c e s. M e ta l-m e ltin g fu rn a c e . S to ra g e - b a tte r y allo y s. M a te ria ls fo r p re c is io n m a c h in ery . N i-C r re s is ta n c e a llo y s. P e r m a n e n t m a g n e ts . W elds a n d w e ld in g . D e te c tin g fa u lty jo in tin g . M g a n d its allo y s. O x id e film s on A l.
R a d io g ra p h y of ste e l. H a rd e n in g h ig h -s p e e d ste e l. N ic k e l-d ip p in g F e . X -R a y d iffra c tio n s tu d y of fa tig u e of m e ta ls . E x a m in in g m e ta l su rfa c e s. M e ta l-m e ltin g fu rn a c e . S to ra g e - b a tte r y allo y s. M a te ria ls fo r p re c is io n m a c h in ery . N i-C r re s is ta n c e a llo y s. P e r m a n e n t m a g n e ts . W elds a n d w e ld in g . D e te c tin g fa u lty jo in tin g . M g a n d its allo y s. O x id e film s on A l.