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BRITISH CHEMICAL ABSTRACTS

B.—A P P L IE D C H E M IS T R Y

AUG. 30, 1929.

L -G E N E R A L ; PLANT; MACHINERY.

Flow of m ercury vapour through nozzles.

W. J. Kearton (Inst. Mech. Eng., June, 1929. Advance copy. 33 pp.).—The mass discharge of mercury vapour through a convergent-parallel nozzle is shown to be in excess of the theoretical value for stable expansion in thermal equilibrium when the initial superheat is below 10°, but compatible with expansion in the supersaturated state down to the throat pressure, with nozzle efficiencies of 85—95%. The apparently excessive mass discharge is not due to the presence of liquid particles. Data from search-tube experiments are consistent with expansion of vapour in the supersaturated state, but inconsistent with expansion in the saturated state. Whatever degree of supersaturation is reached in the first stage of the flow process, the vapour never reverts to the saturated state. Qualitative tests indicate the possibility of super- saturation of the order of 2000 being reached before the establishment of thermal equilibrium begins.

C. J. Sm it h e l l s. Condensation of steam . D. F. Othmer (Ind. Eng.

Chem., 1929, 21, 576—583).—The effect of temperature, concentration of small amounts of air, and of tempera­

ture drop on the rate of condensation of steam on an isothermal condensing surface has been studied. Within the limits of experimental error (using steam at 100—

115° and percentages of air up to 11 • -1%), various empirical relationships were obtained which are expressed mathematically. The results obtained show that a rise in temperature of the steam causes the value of the coefficient of heat transfer from the steam to the con­

densing surface to rise. This is due to the fact th at the viscosity of the condensed water film decreases with rise in temperature, thus increasing the rate of drainage of the water from the condensing surface. In addition, the thermal conductivity of the water film increases with the temperature. H. Ingleson.

Extended steam tables. II. L. Ca l len d a r (Inst.

Mech. Eng., June, 1929. Advance copy. 21 p p .; cf.

A., 1928, 1179).—Extended steam tables for saturated steam a t 400—717° F. and 400—3200 lb./in.2 and for superheated steam at 400—1000° F. and 400—4000 lb./in.2 are given, together with other tables arranged both on a temperature and on a pressure basis, in both Fahrenheit and Centigrade units. C. J. Sm it h e l l s.

Gravitational flow of fertilisers and other com ­ minuted solids. W. E. De m in g and A. L. Me h r in g

(Ind. Eng. Chem., 1929, 21, 661—665).—The rate of flow of comminuted solids, such as potassium nitrate pellets, crystallised monoammonium phosphate and urea, glass beads, lead shot, marbles, crushed phosphate rock, and several types of seeds, from bins or hoppers

depends on the average particlo size, the kinetic coeffi­

cient of friction, and apparent density of the material, the diameter of the aperture, and the vertical angle of the hopper or, if all the material does not flow out, on the angle between opposite slopes of the remaining material. A mathematical expression is derived for the rate of such gravity flow and is found to agree satis­

factorily with practice. D. F. Twiss.

Two pieces of apparatus for m easuring the sp.

gr. of liquids by m eans of a hydrom eter. P . F o c h s (Chem.-Ztg., 1929, 53, 526—527).—To measure the sp. gr. of a hot liquid in a shallow basin by means of a hydrometer, the instrument is placed inside a narrow cylinder open at the lower end and terminating in a narrow tube at the upper e n d ; the lower end of the cylinder is placed below the surface of the solution, and by applying suction to the tube the liquid is drawn into the cylinder until th e , hydrometer floats. In using a hydrometer in a narrow cylinder the instrument may be prevented from touching the walls by placing over its narrow upper tube a small copper wire ring with three arms at angles of 120° to one another, the arms being bent so that when the wire rests on the cylinder the ring is directly over it3 longitudinal axis.

A. R. Po w e l l. Pa t e n t s.

Furnace. I. Ha r t e r, Assr. to Fu l l e r- Le h ig h Co.

(U.S.P. 1,712,919,14.5.29. Appl., 16.12.25).—The walls of the furnace are double with an air space between, through which cooling air circulates; cooling of the inner walls is accelerated by backing the refractory tiles of which it is built up with thin metallic sheets having numerous projections extending into the cooling space.

A. R. Po w e l l. Regenerative furnaces. Woodall- Duckham(1920), Lt d., and M . H. McEw a n (B.P. 314,171, 28.4.28)—In regenerative furnaces which are adapted to burn either lean gas (which is preheated in a manner similar to the air) or strong gas (which is not preheated, thus releasing additional regenerator settings for preheating air), the inlet valves which determine whether lean gas or air passes to the regenerators are separate from the inlet valves which are used in turn with exhaust valves to effect reversal. B. M. Ve n a b l e s.

H eat-exchange apparatus. R. V u i l l e u m i e r , Assr.

to S a f e t y C a r H e a t i n g & L i g h t i n g Co. (U.S.P.

1,716,333, 4.6.29. Appl., 14.10.16. Renewed 6.12.20).

—The inner fluid passes through a number of tube coils and the outer fluid between the coils and an elongated container. Each fluid space is filled with beads of conducting material, e.g., copper, to improve the heat transmission. To prevent undesired transmission in

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B r itis h C h e m ic a l A b s tr a c ts —B.

0 6 * Cl. I . — Gb n i b a l ; Pl a n t ; Ma c h i n e r y.

the longitudinal direction, strata of non-conducting "^m aterial is crushed in a vertical annular space between a beads may be introduced. B. M. Ve n a b l e s. hollow rotating hub and a fixed central boss, and ground

Repairing heated structures such as furnaces, retorts, etc. Woodall- Duckham (1920), Lt d., and A. M cD . Duckham (B.P. 313,728, 24.5.28).—A charge of jointing^material isjnserted into a container with an explosive cartridge behind it. The container is placed on a carrier which also includes a nozzle adapted to guide the material into the crack and is provided with a long handle made up of screwed rods; heavier models may also be provided with wheels. After the apparatus has been placed opposite the crack to be sealed, the cartridge is exploded by the heat of the furnace permeat­

ing to it (or electrically if more convenient) and the material is forced rapidly and deeply into the crack.

B . M. Ve n a b l e s.

Heated drum apparatus for desiccating liquids and sem i-liquids. R. Ha d d a n. From He y l-Be r in-

g e r Fa r b e n f a b r. A.-G. (B.P. 313,817, 5.9.28).—A heated drum is supplied with a layer of the material by two (or more) feed rollers in series, the object of the intermediate roller(s) being to prevent the first roller (which dips into the feed tank) from becoming too hot by conduction from the heated drum.

B. M. Ve n a b l e s.

Freezing of colloidal liquids. B. P. Tsit o v it sc h

(B.P. 288,310, 4.4.28. Esthonia, 8.4.27).—The colloidal liquid such as milk, fruit juices, medicinal sera, beverages, is instantaneously frozen by being delivered in a finely- divided state into an air chamber in such a manner that no movement of the air is induced, the chamber being maintained below the f .p .; the settled finely-divided solid or snow is stored at a temperature below its m.p.

until such time as it is desired to resume its original condition, which it will do, with its flavour etc. unchanged, by simple thawing. B. M. Ve n a b l e s.

Crusher. H. H. Ru m p e l, Assr. to Sm it h Eng

Wor ks (U.S.P. 1,717,894, 18.6.29. Appl., 22.8.27).—

The crushing motion is similar to that of a gyratory crusher, but the vertical shaft rotates without gyration at its lower part in bearings in the lower fixed part of the crusher; the upper part of the shaft is obliquely cranked and carries the crushing head on bearings permitting the shaft to rotate independently of the head.

B. M. Ve n a b l e s.

Crushing m ills. E. C. Lo esch e (B.P. [a] 313,690, [B, c] 313,844—5, [a, b] 14.4.28, [c] 7.1.29).—(a) A concave dish is rotated about a vertical axis, and a roller engages with the interior at the circumference where the surface is rising outwardly. The roller runs on an axis that is fixed except th at it is pressed downwards by spring pressure. The ratio of the diameters ro ll: dish must not exceed 1:2-5, and preferably should not exceed 1 :2 . An upstanding rim may be provided at the edge of the dish, (b) The roller is not allowed quite to touch the dish, a definite stop being provided, (c) Outside the dish and fixed to it are a number of inclined vanes which lift material that has dropped into the containing casing and return it to the grinding zone.

B. M. V e n a b le s .

Crushing, grinding, or m illing apparatus. R E T r o t t i e r (B.P. 296,723, 3.8.28. Fr., 6.9.27).—T h e

in a horizontal annular space between the above two parts extended outwards, this space being provided with balls which are located in “ concentric rings but are not constricted in grooves. B . M. Ve n a b l e s.

Grinding, crushing, pulverising, or disintegrat­

ing m ills. W. A. Cloud (B .P . 313,656, 16.3.28).—A rotating mill is divided into a number of short cylindrical sections increasing in diameter as the grinding progresses.

The linings may be fluted and each section may contain one or more correspondingly fluted grinding rollers. If several rollers are used they are held apart by links and pins, and may be provided with springs to increase the pressure. Radial partitions are provided between each pair of zones, preferably double-walled, with lifting scoops in the spaces between. The holes for transfer of material preferably become larger in the direction of travel. The outlet is axial and an indirect air draught may be used, also a screen to prevent exit of large particles.

B . M. Ve n a b l e s. M ixing solids with liquids. W. Ev a ns (B .P . 314,261, 10.8.28).—A continuous measured stream of finely-divided solids (which may be air- or gas-borne) is projected at high velocity against the surface of a measured stream of the liquid. The solid and the whole of the liquid may be admitted together into a downtake compartment partitioned off from a large tank, or the solid may be projected on to the surface of a pool formed in the stream of part only of the liquid and the carrier gas, partly deprived of its solid content, scrubbed in a tower or other device by another partial stream of liquid, the above two streams then being combined and added to the remainder of the liquid. B . M. Ve n a b l e s.

Apparatus for continuously treating liquids.

A. E . Flo w e r s, Assr. to De Laval Se p a r a t o r Co.

(U.S.P. 1,701,068, 5.2.29. Appl., 22.6.26).—The fluid and other material are mixed and circulated continuously through partitions devised to divide the mixture into thin layers inclined a t an angle substantially less than the angle of repose of either material, so that the lighter material or fluid is removed continuously a t one end, and the heavier discharged at the other.

R. Br ig h t m a n. Filtering m aterial. H . Blu m e n b e r g, j u n. (U.S.P.

1.702.104.12.2.29. Appl., 10.8.27. Renewed 22.12.28).

—Calcium hypochlorite is incorporated with 5—10%

of sodium carbonate and about 70% of diatomaceous earth for use in the filtration, e.g., of mineral oil dis­

tillates, industrial waste waters, sewage, etc.

R. Br ig h t m a n. Continuous-filter thickening apparatus. A. L . Ge n t e r, Assr. to Ce n t e r Th ic k e n e r Co. (U.S.P.

1.716.040.4.6.29. Appl., 16.10.25).—A Genter thickener is provided with a common filtrate receiver situated centrally among a number of banks of filter elements which may or may not be in separate containing vessels.

Connexions with timed valves are so arranged that the filter elements are discharged by pressure in small groups a t a time, the vacuum remaining on the other

groups. B . M. Ve n a b l e s.

Evaporator. B . S. and S. Hu g h e s (U.S.P. 1,717,927,

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B r itis h C h e m ic a l A b s tr a c ts —B .

Cl. I . — G i N B i u i ; P l a i t ; M a o b x s e s t . 665

18.6.29. Appl., 8.3.26).—A shell is divided into an upper and a lower chamber with a tubular heating unit between the two. The charge of material in the lower chamber is pumped (or otherwise lifted) to the top of the heating unit, and evaporation takes place on the downward flow of the liquid. The rising pipe from the pump is centrally placed within the heating unit and is surrounded by an unobstructed large tube for ascen­

sion of the vapour. B. M. Ve n a b l e s. Device for preventing the boiling over of liquids which produce foam when boiling. D. He y n is

(U.S.P. 1,709,529, 16.4.29. Appl., 29.4.27. Holl., 30.3.26).—The liquid is heated in a removable receptacle of such shape as to cause a lateral displacement of the centre of gravity of its contents when foam is produced.

The receptacle is mounted on a platform which is tilted through a small angle by the raising of the foam, and the heating, is controlled in response to the tilting movement of the support. R. Br ig h t m a n.

Arrangement for cooling liquids or fluids.

H. Ma g er (U.S.P. 1,717,237, 11.6.29. Appl., 8.7.25.

Austr., 7.2.25).—To reach a discharge chamber from a chamber placed immediately above, the fluid passes through a number of vertical cylinders, the end walls of which have holes arranged in a circle, registering with holes in the upper and lower chambers. The cylinders are arranged in pairs, the members of each pair rotating in opposite directions. P. G. Cl a r k e.

Gas and liquid contact apparatus. F. W. Sp e r r, Ju n., Assr. to Ko p p e r s Co. (U.S.P. 1,715,252—3, 28.5.29.

Appl., [a] 8.12.21, [b] 9.4.25).—A tower is charged with alternate strata having distributive and contact func­

tions, respectively. In (a) the distributors are regularly arranged short vertical tubes with spiral vanes within, more than one layer being provided for each distributive stratum, and the contact strata are formed from irregu­

larly arranged fragmentary material. In (b) both sorts of strata may be formed from rectangular bars of wood or other m aterial; the bars of successive layers are placed at right angles forming a gridwork, and there are several layers to each stratum. The distributive bars are arranged with their diagonals vertical (and hori­

zontal) ; the contact bars are preferably oblong in section and have their long axes vertical.

B . M . Ve n a b l e s. Apparatus for bringing gaseous and liquid materials into contact. W. H. Ca m p b e l l (B.P.

313,983, 16.3.28).—Ribs are formed on the under­

sides of a number of flat plates which are piled together, the ribs are of varying depths to cause a slope on the plates when piled, and the channels between the ribs become deeper and narrower in the direction of flow of the liquid, which is zig-zag in both horizontal and vertical views, and countercurrent to the flow of gas.

The apparatus is suitable for the cooling and crystallising of a liquid with or without evaporation. The ribs of a plate above may bed on a sheet of rubber or other soft packing placed on the flat surface of a plate below, the rubber preventing both leakage and formation of a solid cake of crystals. B. M. Ve n a b l e s.

Apparatus for condensing m ercury or other vapour and vaporising water or other liquid.

Br it. T h o jis o n - H o u s to n Co., L t d . , Assees. of A. R S m ith (B .P . 303,013, 21.12.28. U .S ., 24.12.27).—The mercury is condensed on the outer walls of a bundle of tubes with headers at each end. As this steam-boiler unit will be subjected to very great expansion and contraction relative to the containing shell, yieldable sealing plates are provided between the boiler headers and the shell; the form shown is S-shaped in section forming short bellows. One shell may be provided for each boiler unit, or several boilers may be placed in one non-circular shell; in the latter case shields partly surround the tube bundles, openings being left facing the mercury inlet to effect uniform distribution of the mercury vapour. B . M. V e n a b l e s .

Catalytic apparatus. Se l d e n Co., Assees. of A. 0.

Ja e g e r(B.P. 301,491 and 301,799, [a] 6. and [b] 20.11.28.

U .S ., [a] 2. and [b] 5.12.27).—Two types of plant involv­

ing the principle of the double countercurrent heat- exchange described in B.P. 306,884 (B., 1929, 672) are

illustrated. C. Ho l l in s.

Vertical drying and dehydrating apparatus. M.

Ba e c h l e r, Assr. to Ba e c h l e r, Kis e r & Ci e. (U.S.P.

1,718,104, 18.6.29. Appl., 26.11.27. Fr., 4.12.26).—

See B.P. 281,664; B ., 1928, 696.

Comm inuting solid substances. W . Os t e r m a n n, A ssr. to In d u s t r ia l Sp r a y Dr y in g Co r p. (U .S .P . 1,718,184, 18.6.29. Appl., 13.7.28. G er., 18.5.23).—

See B.P. 216,110 ; B., 1925, 1.

Apparatus for separating m aterials of different density. J. W. Ha r t l e y (U.S.P. 1,717,707, 18.6.29.

Appl., 2.4.28. U.K., 4.4.27).—See B.P. 293,137; B., 1928, 658.

Air and gas w ashers and hum idifiers. C. S.

Ha n sa rd and A. E. Ne t z e l (B.P. 314,283, 22.9.28).—

See U.S.P. 1,691,971 ; B., 1929, 80.

Autom atic-stoker retort furnaces. G. W . John­

son. From Am e r. En g in e e r in g Co. (B.P. 314,624, 23.4.28).

Furnace w alls. Am e r. En g in e e r in g Co. (B.P.

305,010, 7.5.28. U.S., 2S.1.28. A d d n . to B.P. 297,094).

Refrigerating m achines. Br it. Tiiom son-Houston

Co., Lt d., Assees. of C. St e e n s t r u p (B .P . 293,394, 4.7.28. U.S., 5.7.27).

Refrigerating sy stem s and apparatus. Fr ig id-

a ir e Co r p., Assees. of H . B. Hu l l (B.P. 299,028, 23.1.28.

U.S., 20.10.27).

Absorption refrigerating m achines. Su l zer

Fr e r e sSo c. An o n. (B.P. 295,009,17.5.28. Switz., 6.8.27).

Compression refrigerating apparatus. J. A.

Gr ie r and J. A. Wa r r e n (B.P. 288,138, 19.3.28. U.S., 31.3.27).

Bag filters for cleaning air. Ma s c h in e n f a b r. Be t h A.-G. (B.P. 314,297, 31.10.28. Ger., 1.10.28.

Addn. to B.P. 281,994).

Mixed liquids and power generation (U.S.P.

1,716,130). Rem oving carbon dioxide and hydrogen sulphide from gas m ixtures (B.P. 286,622).—See II.

W alls, furnaces, etc. of refractory m aterials (B.P.

287,556).—See VIII. Chemical balance (U.S.P.

1,717,462).—See XI.

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B r itis h C h e m ic a l A b s tr a c ts —B .

6 8 6 Cl. I I . — Fttel ; Ga s ; Ta b ; Mi n e r a l Oi l s.

n .— FU E L ; G A S; T A R ; MINERAL OILS.

Influence of m ineral constituents and especially iron oxide on the hydrogenation of coal. B.

Hlavica (Brennstoff-Chem., 1929, 10, 201—203; cf.

B., 1928, 629).—A low-ash coal ” prepared by heating starch at 300° in an autoclave yielded only 6-2% of oil on hydrogenation. The yield, however, was increased to 13-0% in the presence of 23-9% of zinc chloride.

The ash of ordinary coals contains varying amounts of iron compounds, of which pyrites has an especially marked catalytic effect on the hydrogenation. The addition of ferric oxide to coal increases the oil yield on hydrogenation, its influence being greater with bituminous coals than with brown coals or lignites.

A. B. Ma n n in g. Bitumen and the water-soluble and pyridine- soluble constituents of som e brown coals. H.

St k in b r e c h e r (Brennstoff-Chem., 1929, 10, 198—201 ; cf. B., 1927, 593).—A number of brown coals have been extracted successively with a benzene-alcohol mixture, water, and pyridine. Large variations were observed in the amounts of bitumen (G- 3—-36-6%) and water- soluble ash (0-8—5-5%) which were extracted. The bitumen was resolved into a benzene-insoluble wax, an acetone-insoluble wax, and an acetone-soluble resin.

There appeared to be a relation between the resin content of the coal and the explosibility of its dust.

Considerable variations were observed in the acid, saponification, and esterification values of the bitumens.

The water-soluble ash consisted of varying mixtures of sodium, calcium, magnesium, iron, and aluminium sulphates. The pyridine extracts were soluble in dilute alkaline solutions from which they were repre- cipitated by acids ; in chemical and physical properties they closely resembled the humic acids derived from brown coals. Treatment of the coals with pyridine reduced the ash content, partly by dissolution and partly by mechanical separation due to the swelling and consequent loosening of the material.

A. B. Manning. Importance of the low-tem perature assay in the investigation of coking coals. P. Damji (Brennstoff- Chem., 1929, 10, 191—195, 217—221 ; cf. B., 1929, 382).—The coking process may be divided into three stages, the preheating stage, the plastic stage, and the final distillation. Fischer’s aluminium assay apparatus has been used to study the changes occurring in each of these stages for a number of coals. In particular, the changes in caking index and swelling pressure on heating the coal at a temperature 25° below its softening point have been determined, and the cokes produced by carbonising the original coal and the preheated coal at 500° have been compared. Coals of the same oil and solid bitumen content and the same caking index may show marked differences in behaviour during the preheating period. The greater are the changes observed during this period the greater is the influence of the rate of heating on the coking process. The length of the temperature interval corresponding with the plastic stage has an important influence on the coke structure ; the more is the volatile m atter evolved during the plastic stage the less remains to be evolved during the final distillation and the less fissured is the

coke. No satisfactory method, however, has yet been devised to determine accurately the temperature corresponding with the end of the plastic stage.

A. B. Manning.

Determination of sulphur in coal. N . A. Nikolai and N . Vorobiev (Izvestia Teplotech. Inst. [Moscow], 1929, N o. 3, 91— 92).— Weighed samples of coal are burned in a calorimetric bomb in an atmosphere of oxygen under a pressure of 20— 25 atm . The bomb contains also a few c.c. of a 10% solution of sodium carbonate to remove any oxides formed and to facilitate the subsequent separation of iron. After allowing to cool for 5— 10 min. the residual gas is allowed to escape, the contents are poured out into a beaker, the bomb is washed several tim es w ith warm distilled water, and the combined washings are filtered, th e sulphur being determined by Eschka’s method. Comparative tables are given of th e results obtained b y Eschka’s method, by the author’s “ bomb-washing ” m ethod, and b y the sodium peroxide m ethod. The results obtained b y the first two methods agree fairly closely. A . Freijian.

Hardness and structure of coke. R. A. Mott

(Fuel, 1929, 8, 322—333).—The production of breeze during the transport of coke from the oven to the blast furnace takes place mainly when the coke is dropped into the wagons, hoppers, or into the furnace itself.

The shatter test, which gives a relative measure of the liability of different cokes to form breeze in this manner, shows th a t the effect of one large drop is the same as that of a number of smaller drops from the same aggregate height. In successive drops through the same height, however, the breakage decreases. The shatter index may be expressed either as the percentage remaining on a 2-in. or on a l|- in . mesh sieve. For nonnal cokes there is an approximately linear relation­

ship between the two indices. In general, the l|-in . index is to be preferred, but for research purposes it is recommended th at both, and the 1-in. index as well, be determined. South Wales cokes exhibit the highest indices (average 96-6), Derbyshire cokes the lowest (average 69-7). A close relationship exists between the shatter index and the number and definition of the fractures in the coke shown by Rose’s method of studying the structure (B., 1925, 834). Large-scale coking tests show that, in general, the hardness of the coke is im­

proved by “ top-charging ” the coal instead of com­

pressing it. A rapid rate of heating may be disadvan­

tageous when coking a high-volatile strongly caking coal. The hardness of the coke increases to an extent with decrease in the size of the coal u se d ; there is, however, no advantage in extremely fine grinding (100% through ¿--in. mesh). Crushed slack gives a harder coke than crushed large coal, and clean slurry a still harder coke. By blending 20—30% of low- temperature breeze or anthracite duff with a good coking coal the shatter index of the coke may be appreciably

raised. A. B. Ma n n in g.

Flam e speeds and their calculation. W . Pay-

m an and R. V. Wh e e l e r (Fuel, 1929, 8, 4—9, 91—98, 104—114, 153—162, 204—219).—The evidence for the

“ law of flame speeds ” (B., 1922, 359 a) is collected and discussed in detail (cf. B., 1923, 42 a, 436 a, 437 a, 757 a;

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B ritish C h e m ic a l A b s tr a c ts —B .

Cl. I I . — Fu e l ; Ga s ; Ta b ; Mi n e r a l Oi l s. 667

A., 1926, 689 ; 1927, 317, 630). The method of applica­

tion of the law to complex gaseous mixtures is described.

A. B . Ma n n in g. Rapid method of determ ining the m axim um adsorption of benzene by activated charcoal. H.

Bu r st in and J. Win k l e r (Brennstofi-Chem., 1929, 10, 121—124).—The relationship A„mx. = KQ, between A- max., the maximum amount of benzene which a sample of activated charcoal will adsorb from a current of air saturated with the vapour, and Q, the heat of wetting of the charcoal by benzene, which may be deduced from theoretical considerations, has been verified experi­

mentally. If Q is expressed in' kg.-cal./g. and A maI- as a percentage, the value of the constant is 1-9. If, therefore, Q be determined A max. may be calculated.

Q may be determined conveniently in a small, vacuum- jacketed vessel through the stopper of which passes a thermometer graduated in 0-1°. Benzene (10 c.c.) is introduced into the vessel, and the temperature, which is preferably adjusted to be about 20°, is read. Then 2 g. of the dry charcoal at the same temperature are added and the vessel is shaken for \ min., which is usually sufficient for the temperature to attain equi­

librium. Q is calculated from the observed rise in

temperature. A. B. Ma n n in g.

Industrial process for obtaining liquid hydro­

carbons by sim ultaneous cracking and hydro­

genation [“ Sem o ” process]. J. Fo k len (Chim.

et Ind., 1929, 21, 1141—1148).-—Cracked oils and hydrogen, without condensation, are led a t ordinary pressure through purifiers at 300—250° to a series of reduced nickel catalysts maintained a t 250—170°

without external heating. Lignites, shales, and other poor or sulphurous starting materials give good results.

The purifying agents are similar in composition to the catalyst used, and serve to remove all catalyst poisons ; since the removal is an exothermic reaction there need be little loss of heat. In the initial catalyst vessels the temperature is sufficient to destroy any phenols present.

A Greek lignite giving by cracking alone an oil of which only 52% distilled below 320° (23-5% below 220°) yielded by this “ Semo ” process a much lighter oil (94% below 300°, 74% below 220°, distillation begin­

ning at 42°). C. Ho l l in s.

Air oxidation of hydrocarbons catalysed by nitrogen oxides. C. H . Bib b and H . J. Lucas (Ind.

Eng. Chem., 1929, 21, 633—638).—Natural gas con­

taining 85% of methane was bubbled through con­

centrated nitric acid at 10° and then passed with 2-5—7-0 vols. of air through an electric furnace.

Conversions of up to 5% of carbon into formaldehyde were obtained. The highest concentration of formalde­

hyde in the condensate (25%) was found with a furnace temperature of 750°, a time of passage of 0-13 sec., and low air-hydrocarbon ratio. The catalytic oxidation of benzene vapour was studied similarly. The exit gases were scrubbed with light lubricating oil to remove benzene and phenols, and the phenol was determined as tribromophenol. Conversions up to 5% were again obtained,rbut a smaller yield was neceesary in order to avoid the formation of carbon dioxide. With a 3-5%

conversion a yield of 52% of benzene as phenol was

obtained. In this case the nitric acid is best maintained at 40°. Theoretical reasons for the superiority of oxides of nitrogen over solid catalysts are discussed.

C. Ir w in. Acids of montan w ax. D. Ho l d e, W. Bl e y b e r g, and H. Vo h r e r (Brennstoff-Chem., 1929, 10, 101—108, 124—128).—By fractional distillation under reduced pressure of the ethyl esters of the acids from montan wax, followed by fractional crystallisation of the acids themselves and fractional precipitation of their lithium salts, an acid C28H560 2 (m.p. 84-4°) has been isolated in the pure state, and the presence of the iso-acid Ca2H640 2 (m.p. 89°) and probably also of an acid C30H60O2 has been established. No evidence was found of the presence of the acid C29H580 2 (cf. Tropsch and Kreutzer, B., 1922, 659 a). A. B . Ma n n in g.

Decolorisation of cresols. Rakovski and Me h l.—

See III. Absolute alcohol from sulphite-spirit.

Kir m r e u t h e r.—See V. Dissociation of carbon m on­

oxide. Hu b ba rd and Re e s.—See VII. Silica bricks.

Re e s and Hu g il l. Refractories for carbonisation plant. Da l e and others.—See VIII. Saponification values. Nor m a n n.—See X II.

Pa t e n t s.

Pulverising apparatus for solid fuels etc. G. S.

Loy (B.P. 300,561, 14.11.28. Fr., 14.11.27. Addn. to B.P. 190,132 ; B., 1923, 917 a. Cf. also B.P. 234,366 ; B., 1925, 576).—The apparatus described in the main patent is modified in th at the movable grinder is formed by a plate on one face of which hollow pins are so mounted that their free ends engage the stationary grinder. The face of the latter is provided with metallic wires arranged in the direction of the axis of rotation.

A. B . Ma n n in g. Coke oven by-product recovery sy stem . Ba r­

r e t t Co., Assees. of S. P . Mil l e r (B .P . 298,153, 6.9.28.

U.S., 4.10.27).—The hot coke-oven gases are subjected to a regulated cooling, e.g., by sprays of ammonia liquor in the goose-necks and collector main, to such a temperature th at a pitch of a desired m.p. separates from the gas, which, while being maintained at the same temperature, is scrubbed with hot pitch of similar composition to th at carried in suspension in the gas.

The residual oils in the gas are subsequently recovered therefrom in a suitable condensing system.

A. B . Ma n n in g. Burning of fuel. T . M. Ch a n c e (U.S.P. 1,716,815, 11.6.29. Appl., 1.2.27).—Before being burned, the coal is mixed with the unfused portion of the ash, to reduce clinkering, this ash being recovered after each com­

bustion. F. G. Cl a r k e.

D istillation of wood. R . H. Tw in in g, Assr. to Cl e v e l a n d-Cl if f s Iro n Co. (U.S.P. 1,716,745, 11.6.29.

Appl., 12.12.24).—Wood is distilled in a retort and the issuing vapours are subjected to the countercurrent scrubbing action of hot, crude pyroligneous acid from such distillation and from which tar has been settled.

H. S. Ga r l ic k. Manufacture of carbon black. R . H . Uh l in g e r, Assr. to Th erm a to m ic Carbon Co. (U.S.P. 1,707,775, 2.4.29. Appl., 12.5.26).—The mixture of gases and

(6)

B r itis h C h e m ic a l A b s tr a c ts —B .

668 Cl. I I .— Fu e l ; Gas ; T ab ; Mi n e r a l Oi l s.

c a rb o n b la c k fro m th e d e c o m p o sin g fu r n a c e is s u b je c te d t o a s p r a y o f cooling liq u id , a n d th e n c e p asses in to s e p a r a tin g c h a m b e rs w h e re th e d e p o s ite d c a rb o n b la c k is freed fro m m o is tu re b y c o n v e y in g i t in c o u n te r- c u r r e n t w ith t h e m ix tu r e of gases a n d c a rb o n b la c k leav in g a d eco m p o sin g fu rn a c e . R . Br ig h t m a n.

Production of hydrogen and carbon by thermal decom position of hydrocarbons. A. W . Bu r w e l l, Assr. to Al o x. Ch e m. Co r p. (U.S.P. 1,717,354,18.6.29.

Appl., 22.8.27).—After a preliminary heat-treatment, the vaporised hydrocarbons enter the decomposition zone of a cyclic stream of heated inert gas. The gaseous products containing hydrogen and carbon pass through a settling chamber for the removal of the latter, and the portion of the gas stream in excess of th at required for re-use is then withdrawn from the cycle. The remainder is heated to a t least 1200° and introduced into the decomposition zone. F. G. Cl a r k e.

Production of w ater-gas. C. W. An d r e w s and IL A. Br a s s e r t (U.S.P. 1,701,253, 5.2.29. Appl., 15.7.22).—Carbonaceous material, e.g., coke, is air- blasted to the desired temperature, a layer of coal is placed on the heated residue, and the whole is blasted with steam, the coal layer being agitated. The process is continued with air-blasting before each addition of

coal. R. Br ig h t m a n.

Production of oil-gas. F. T . Ne w it t, S. H. La

Pl a n t, and L . I. Tu r n e r, Assrs. to L .T .N . Ma n u f a c­

t u r in g & Dev e l o p m e n t Sys t e m (U .S .P . 1,701,892, 12.2.29. Appl., 11.3.24).—Oil, e.g., gasoline, is atomised by opposition discharge into a larger steam-discharge nozzle, provided with control valve and baffle plate, the oil-gas being drawn off continuously through a pipe provided with check valve, and used in part to generate

the steam. R. Br ig h t m a n.

Removing readily absorbed gases, m ore par­

ticularly carbon dioxide and hydrogen sulphide, from gas m ixtures by absorption in water under pressure. Ge s. f. Lin d es Eis m a s c h in e n A.-G. (B.P.

286,622, 5.3.28. Ger., 5.3.27).—The gas is washed in two towers in succession. In the first the hydrogen sulphide is almost completely removed by washing under pressure with part of the water, saturated with carbon dioxide etc., withdrawn from the second tower, in which the carbon dioxide is removed from the gas by washing with regenerated fresh water. The water from the first tower is regenerated by reducing the pressure and, if necessary, subsequently removing the last traces of hydrogen sulphide by a chemical treatment, e.g., with ferric oxide or sulphur dioxide ; or, after permitting the pressure to fall to normal, the residual hydrogen sulphide may be removed by passing a current of a gas rich in carbon dioxide through the water. The hydrogen sulphide in the gases so recovered is converted into sul­

phur, e.g., in a Claus furnace. To prevent corrosion of the metal of the apparatus a small proportion of an alkaline carbonate is added to the water.

A. B. Ma n n in g. Gas-purification solution and process. W. H . Hil land|D. L. Jacobson, Assrs. to Ko p p e r s Co. (U.S.P.

1,700,982, 5.2.29. Appl., 13.7.25).—In a cyclio process

for purifying gas from hydrogen sulphide, humic sub­

stances are added to the washing liquid to accelerate the oxidation of the iron sulphides etc. in regenerating the iron oxide. E.g., filtered solution (300 gal.) obtained by extracting ground peat with an equal volume of 9%

sodium carbonate solution are added to 9% sodium carbonate solution (100 gal.), and freshly precipitated ferric compounds are added to give a suspension con­

taining up to 1% of ferric oxide. R. Br ig h t m a n. Production of w ater-gas and extraction of oil from oil shale. A. Sc h il l in g, R. Sa c h s e, D. Lia m in, and T. Ca l l a e r t (U.S.P. 1,716,667, 11.6.29. Appl., 26.8.26).—A confined charge of oil shale is ignited at its upper surface, and steam and combustion gases are drawn downwardly through the shale, decomposition setting in to produce water-gas and hydrocarbon vapours. The water-gas is used to generate the steam required, whilst released oil is collected and the hydro­

carbon vapours are condensed. Air for combustion is admitted to the upper surface of the ignited shale in quantity automatically controlled in accordance with the temperature of the water-gas. H . S. Ga r l ic k.

Treatm ent of bitum inous m aterial. W. H.

Ham pt o n (U.S.P. 1,707,759, 2.4.29. Appl., 17.12.19).—

Bituminous shale is crushed, mixed with preheated kerosene or other light mineral oil, and ground. The fluid mixture is conveyed through a series of digesters of increasing temperature up to, e.g., 340—360°, in the final digester, which is maintained a t 100 lb./in.2 or less.

Vapours from the digesters are drawn by a steam injector into cracking coils a t about 700°, the cracked vapours being condensed and fractionated. The residual digestion mixture is discharged through a heat exchanger to a centrifuge, and the solid m atter is washed with light solvent, dried, and discarded or returned for re-treat­

ment. The oil and washings from the centrifuge are circulated through the heat exchanger and fractionated by discharge through a rose into a topping tower, vapours from which, pass to the fractional condensing columns, while the heavier oil from the base of the tower may be circulated to the oil supply tank for mixing with fresh bituminous material. R. Br ig h t m a n.

Apparatus for conversion of hydrocarbons.

L . C. Hu f f, Assr. to Un iv e r s a l Oil Products Co.

(U.S.P. 1,716,136, 4.6.29. Appl., 23.2.24).—A still, arranged in a furnace, has a series of conduits extending along its exterior lower surface connected to similar conduits extending along its inner lower surface. Steam supplied to the former passes on through the inner conduits, which are so perforated th a t the steam is directed against the lower interior surface of the still, whereby direct application of extremely hot combustion gases and consequent coke deposition is avoided.

H . S. Ga r l ic k. Apparatus for treating [cracking] hydrocarbons.

L . d e Flo r ez, Assr. to Te x a s Co. (U.S.P. 1,715,643, 4.6.29. Appl., 8.7.19. Renewed 6.7.28).—The apparatus comprises a heating chamber containing a series of tubes in which the oil is cracked, the tubes in the hotter zones of the chamber being of smaller cross-section than those in the cooler so as to increase the velocity of the vapours through the hot zones and thereby prevent

(7)

B r itis h C h e m ic a l A b s tr a c ts —B .

Cl. I I . — Fu e l ; Ga s ; Ta b ; Mi n e r a l Oi l s. 6 6 9

d ep o sitio n of c a rb o n in th e tu b e s . T h is v e lo c ity is fu r th e r in c re a se d b y p a ss in g b a c k a q u a n ti ty of t h e gase­

ous p ro d u c ts of c ra c k in g in to th e w id e r tu b e s of th e a p p a r a t u s ; th i s p ro c e d u re also re d u c e s th e p ro p o rtio n of h e a v y h y d ro c a r b o n o il c o n v e rte d in to gaseo u s h y d ro ­

carbons. A . R . Po w e l l.

Apparatus for chem ically treating natural oils.

J . L. Taylor a n d C. L. Ho w s e r (U.S.P. 1,717,744, 18.6.29. Appl., 26.10.26).—The treatment liquid from a supply tank is mixed with the oil as it passes through ajnanifold on its way to a boiler. The supply tank is provided with independent air and gas conduits;

the treated mixture passes from the boiler to a settling

ta nk. F. G. Cl a r k e.

Apparatus for treating [cracking] hydrocarbon oils. J. B . We a v e r, Assr. to Gyro Pro cess Co r p. (U.S.P. 1,708,247,9.4.29. Appl., 22.7.25).—Oil is passed from a pipe still at, e.g., 370° and 25 lb./in.2, into an expander, vapours from which pass on, e.g., at 320°, into the header of a convertor, heated to 600°. The converter tubes are filled with ferric oxide or other agent, and residues from the expander are injected with pressure steam. Vapours from the converter are cooled to 230°, the vapours are scrubbed and condensed, and the liquid is returned to the pipe still. 11. Br ig h t m a n.

Cracking of hydrocarbon oils. E. W. Isom, Assr. to Sin c l a ir Re f in in g Co. (U.S.P. 1,708,180, 9.4.29. Appl., 21.5.27).—Hydrocarbon oil is circulated through a heating coil to and from a main supply tank at, e.g., 400—425°. Vapours from the tank pass through two reflux condensers in series; condensate from the first may be returned to the circulating oil or mixed with condensate from the second condenser and heavier feed oil, preheated, and circulated through a secondary coil at, e.g., 540—665°, and a tar trap to discharge from a perforated pipe into the main supply tank. Gas oil or heavy gas oil or fuel oil may be supplied direct to the supply tank, and light gas oil or kerosene to the condensate entering the secondary cracking tube.

R. Br ig h t m a n. Treating [cracking] hydrocarbon oils. G. B . Bogart, Assr. to Te x a s Co. (U.S.P. 1,709,304, 16.4.29.

Appl., 17.2.27).—The hydrocarbon oil is fed into the heating coil and vapours from the cracking stills are discharged to a fractionating column above which is mounted a reflux condenser. Reflux condensate is returned to the column, partly direct, partly after cooling in a coil, and the phlegms from the column are circulated with fresh oil through the heating coil. R. Br ig h t m a n.

Distillation and cracking of hydrocarbons, particularly m ineral oils and tars. H. Magnus

(B.P. 287,525 and Addn. B.P. 313,937, 14.3.28. Ger., [a] 23.3.27).—(a) The process is effected continuously at raised temperatures and pressures in two or more ves­

sels so combined that the liquid constituents and vapours formed in each vessel are separately withdrawn and fractionated in a condensing plant, and the valuable fractions are withdrawn while the remaining fractions are fed into the next vessel in the form of vapour or liquid to be subjected therein to further treatment under higher pressure. The flow created by the excess

of pressure in the reaction vessels relatively to that in the cooling chambers is utilised for generating energy, the gases, vapours, and liquids being allowed to expand either singly or together in a turbine which directly or indirectly furnishes the power required for forcing the fractions to be further treated into the next vessel at higher pressure, (b) The preheated raw material is led to a distributing ring mounted in the distillation vessel and having nozzles arranged in a body of molten metal which partly fills the vessel and serves to transmit heat from an oil or gas burner. The nozzles are arranged in a tangential direction and serve, together with circu­

lating channels provided in the wall of the vessel which may be covered by a cylindrical insert extending over a great part of the length of the channels or by separate covers, to keep the metal both in a rotary and in a vertical circulation, the rate of which can be increased by injecting carrier gases through some of the nozzles and providing spirally-formed circulation channels.

Electrical contact devices are provided so that, if molten metal escapes the feed supply and new material, valves are automatically closed and cooling air or gases or fluids preventing combustion are driven through the furnace.

H. S. Ga r l ic k. Treating [cracking] fluid hydrocarbons. F . B.

Fr e t t e r, Assr. to Na t. Re f in in g Co. (U.S.P. 1,707,606, 2.4.29. Appl., 18.6.25).—The hydrocarbon oil is sup­

plied to the base of a condensing tower, provided with baffles, where it is heated by mixture with the phlegms, and the mixed oil is pumped rapidly at a higher pressure, e.g., above 1000 lb./in.2, through a tubular heater at, e.g., 425° or above. The pressure is released through a Venturi tube or other accelerating vent, operated by a needle-valve, which discharges the heated oil into a vaporiser, substantially at atmospheric pressure, and the cracked vapouTs escape through a dome and wide pipe to the condensing tower. R . Br ig h t m a n.

Obtaining light hydrocarbons from solid or liquid fuels. P . Gir a r d, F. Pe t it, and A. Ch a r-

b o n n ea u (B .P . 299,861, 16.5.28. Fr., 3.11.27).—The raw material is distilled at 300—650° in the presence of an oxidising agent, e.g., potassium permanganate, manganese dioxide, potassium dichromate, and the vapours are subjected to a high-frequency oscillatory discharge before being condensed. H. S. Ga r l ic k.

Apparatus for treatm ent of m ineral oils. W. F.

Dow n s(M. G. Do w n s, adtrix.) (U.S.P. 1,716,372,11.6.29.

Appl., 24.11.22).—A still, suitably heated, is fitted with a paddle near to the bottom for causing an upward circulation of solid matter tending to settle, and a separate beater mechanism above the paddle for breaking up any such solid m atter which forms as a result of distilling a mixture of mineral oil and aluminium chloride with which the still is charged. The vapours are main­

tained at a temperature above the volatilising point of aluminium chloride while being led to a condenser having a filter bed therein. H. S. Ga r l ic k.

Preparation of products w ith a high benzene content from those with a low content. A. Ott

(F.P. 629,481, 17.1.27. Ger., 18.1.26).—In recovering benzene from wash oils used in scrubbing coal gas, the oil is heated at 200° in the later stages with steam under

b

(8)

B r itis h C h e m ic a l A b s tr a c ts —B .

670 Ol. HI.— Or o a w io In t e r m e d i a t e s.

pressure in jacketed vessels. The condensed water from these vessels has a temperature of 150—160° under 6—7 atm. and its heat content may be utilised for the indirect heating of fresh quantities of oil saturated

with benzene. A. R. Po w e l l.

Motor fuel and its manufacture. L. Kirsc h br a u n

(U.S.P. 1,701,620, 12.2.29. Appl., 8.1.20. Renewed 5.7.28).—Pressure distillate, d 0-7692, obtained, e.g., from Kansas gas oil, d 0-875, by cracking at 400°

and 90 lb. in.2, after fractionation from tar if necessary, is emulsified with naphthenic acid and less than 15%

of water to give fuel for internal-combustion engines.

R. Br ig h t m a n. O il-treating process and apparatus. J. R. Hal l

(U.S.P. 1,718,141, 18.6.29. Appl., 25.5.27).—A centri­

fugal drum set with its axis horizontal is divided by a vertical partition, and comprises two spiral passages which are connected only by a port at the periphery.

Crude oil, forced into one trunnion, enters one of the spiral passages, heavy impurities are ejected at the periphery, through valves which are actuated auto­

matically at a predetermined pressure, and the clear oil passes through the second spiral passage to the other trunnion. P. G. Cl a r k e.

Sim ultaneously separating m ixed liquids of different b.p. and generating power. C. F . Hir s h-

fe l d (U.S.P. 1,716,130, 4,6.29. Appl., 6.3.22).—Mixed vapours, e.g., those from steam-distilled oil shales, are expanded in a turbine or other engine, and liquid fractions are taken off at various stages.

B. M. Ve n a b l e s. Apparatus for drying, charring, and otherwise treating loose m aterial. O. Do b b e l st e in (U.S.P.

1,718,542—4, 25.6.29. Appl., [a] 12.12.24, [b] 6.12.26, [c] 24.10.2S. Ger., [ac] 18.12.23).—See B.P. 226,543 ; B., 1925, 655.

Purification of coke-oven gases and the like.

G. Cla u d e, Assr. to L ’A ir Liq u id e Soc. An o n, po u r l’Et u d e e t l’Ex p l o it. d e s Pro c. G. Claud e (U.S.P.

1,717,761, 18.6.29. Appl., 4.11.26. Fr„ 17.11.23).—

See B.P. 224,863; B., 1925, 308.

Apparatus for manufacture of w ater-gas. H.

Nie l s e n a n d B. La in g, Assrs. to Se n s ib l e He a t

Dis t il l a t io n, Lt d. (U.S.P. 1,718,830, 25.6.29. Appl., 20.9.28, U.K., 28.5.27).—See B.P. 299,485 ; B., 1929, 8.

Doors of horizontal ovens for producing gas, coke, etc. E. Wo l f f (B.P. 314,281, 19.9.28).

Gas or vapour burners. I . Tu r n e r (B.P. 314,721, 7.9.28).

Filtering m aterial (U.S.P. 1,702,104).—Seel. Puri­

fication of sulphur (B.P. 314,697). Gaseous m ixtures containing hydrogen (B.P. 288,577).—See VII.

Carbon electrodes (B.P. 294,176).—See VIII.

ID.— ORGANIC INTERMEDIATES.

Decolorisation of cresols b y hum ic acids. W.

Rakovski a n d P. Me h l (Brennstoff-Chem., 1929, 10, 221—222).—By refluxing crude cresols with 20% of humic acids a n d then distilling, a colourless product is obtained which does not change on exposure to light

for long periods. The humic a "ids may be prepared from peat, or peat itself from which the bitumens have been extracted may be used. From the tar acids of a low-temperature peat tar purified in this manner an appreciable yield of crystalline phenol has been obtained.

A. B. Ma n n in g. Determ ination of sulphuric acid in a mixture of sulphuric acid, acetic acid, and acetic anhydride.

T. Som iya (J. Soc. Cliom. Ind., Japan, 1928, 31, 306—

310).—When barium acetate is dissolved in acetic acid containing a small percentage of acetic anhydride, and the resulting solution used as a standard, the sulphoacetic acid can be accurately titrated thermo- metrically in the presence of acetic anhydride. The standardisation of the barium acetate solution can be carried out thermometrically by titrating against sulphuric acid dissolved in acetic acid solution, which serves equally well whether it contains acetic anhydride

or not. Y. Na g a i.

Benzathrones. J. Ma r t in e t and A. Drobatschev

(Chim. et Ind., 1929, 21, 227—241, 1149-1160).—

A review and bibliography of benzanthrone and its

derivatives. C. Ho l l in s.

Air oxidation of hydrocarbons. Bib b and Lucas.

—See II. Absolute alcohol from sulphite-spirit.

Kir m r e u t h e r.—See V.

Pa t e n t s.

Manufacture of aldehydes and alcohols [from carbon m onoxide and hydrogen]. G. T. Morgan

and R. Ta y lo r (B.P. 313,061, 28.2.28. Cf. Morgan, Taylor, and Hedley, B., 1928, 439).—To the mixed zinc-chromium or zinc-manganese oxide catalysts for hydrogenation of carbon monoxide, cobalt, with or without copper, in reducible form is added. This catalyst is selected as giving a high yield of ethyl

alcohol. C. Ho l l in s.

Purification of alcohols obtained b y the catalysed interaction of hydrogen w ith oxides of carbon.

A. Ca r p m a e l. From h G. Fa r b e n in d. A.-G. (B.P.

311,468, 16.2.28).—The crude alcohol is stirred with a small amount of an oxidant (e.g., 0-15% of perman­

ganate in water) and fractionated, with or without the addition of water and/or alkali or zinc chloride.

The addition of organic bases, such as m-phenyleno- diamine, aminoplienols, or phenylhydrazine, after the oxidation is advantageous. C. Ho l l in s.

Manufacture of acetaldehyde from acetylene or gaseous m ixtures containing it. J . Y. Johnson. From I. G. Fa r b e n in d. A.-G. (B.P. 312,716, 10.3.28).—

Formation of resinous m atter when working at raised temperatures (70—90°) is avoided by using as catalyst for the conversion of acetylene into acetaldehyde an aqueous solution of an alkali hydrogen sulphate con­

taining a mercury compound and a compound of a metal of group I or V I I I ; e.g., aqueous potassium hydrogen sulphate (100 g. S04 per litre) with mercuric sulphate (50 g.) and copper sulphate (4 g.) gives 95% conversion.

C. Ho l l in s. Manufacture of aliphatic [acetic] anhydrides.

H . Dr e y f u s (B.P. 313,418, 10.1.28).—Acetic acid vapour is mixed with sulphur dioxide (5—10%) and

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