baber/WOPTO huggingface dataset:
Patent GB-1359367-A (GB)
Title: Layered complex metal silicate composition their preparation and use  in hydrocarbon conversion reactions
IPC: B01J21/00
Filed: 1971-08-11
Abstract: 1359367 Hydrocarbon conversion catalysts ESSO RESEARCH & ENG CO 11 Aug 1971 [31 Aug 1970 (4)] 37738/71 Heading B1E [Also in Divisions Cl and C5] A layered silicate having the formula where x is 0-1, # is 0-4, and n is 6/[a(1-x)+ bx], a and b being the valencies of M and M<SP>1</SP> resp., is used as a catalyst for hydrocarbon conversions, alone, or impregnated with another metal, and/or composited with a matrix material. M and M<SP>1</SP> may be Mg, Ni, Co. Cr, Mo, W, Pd, Pt, Al, Li, Cu, Zn, Sc, Ga, Ti, Zr, V, Mn, Fe. The silicate may be in the form of tubes or flakes. Specific silicates disclosed are Mg, Ni, Mg, with Co, Ni, Fe, Mn, Cu, Cr, Zn, Al, W, Mo, Pt and Re, Ni/W, Ni/Al, and Co/Mo. They may be impregnated with Cr, Pt, Pd, Mo, W, Ni, Co, or Re compounds, and may be formed into pellets with a binder, calcined. and the metal optionally reduced. The silicate may also be treated with AlBr 3 , AlCl 3 , or HF. The matrix material may be Al 2 O 3 -SiO 2 .
Patent GB-1526041-A (GB)
Title: Sources of x-radiation
IPC: H01J35/08
Filed: 1975-08-29
Abstract: 1526041 X-ray tubes EMI Ltd 29 Aug 1975 [29 Aug 1974] 37743/74 Heading H1D An X-ray tube for generating a planar fan of substantially uniform X-radiation comprises a target surface curved in the plane of the fan, which fan is substantially sideways to the general path of the electron beam, and the electrons being incident over the curved surface at substantially equal angles of incidence. Window 5 selects the required fan, and additional collimation and electrostatic focusing may be provided. The electron beam need not be circularly symmetrical but can be flat. The forward X-ray emission due to higher energy electrons may produce crossing X-ray beams in which case a fan-like array of collimators are used. The electron beam may be directed at an angle to the gun-target axis and converge with substantial positive aberration (bracket B) (Fig. 3, not shown). Beam convergence angles of 30 to 50 degrees are desirable for diagnostic radiology. Each beam is 30 degrees to the anode surface at the point of incidence. Proton input is mentioned.
Patent GB-1508708-A (GB)
Title: Housing for teleprinters or the like
IPC: H05K5/03
Filed: 1976-09-13
Abstract: 1508708 Lid operating mechanism; stays INTERNATIONAL STANDARD ELECTRIC CORP 13 Sept 1976 [24 Sept 1975] 37838/76 Headings E2F and E2M In a housing for a teleprinter, a base 1 has a lid 2 detachably hinged thereto at 3, and a toggle mechanism is disposed between the lid 2 and the base 1 to assist the opening and closing movements of the lid when the mechanism passes a dead centre position denoted by the line 18 in Fig. 1. The arms 4, 7 of the toggle mechanism are separated in the open position of the lid to permit the lid to be detached from the base. The arm 7 of the toggle mechanism is in the form of a push rod 7 slidable in a guide 14 fixed to the base and loaded by a compression spring 12. The push rod 7 is provided with a notch 9 which engages a hole 22 in the guide 14 to retain the lid in the open position.
Patent GB-878622-A (GB)
Title: Improvements in or relating to steroids and the manufacture thereof
IPC: C07J5/00
Filed: 1958-11-25
Abstract: The invention comprises 6-fluoro-9a -halo-21-desoxyhydrocortisone and 6-fluoro-9a -halo-21-desoxycortisone, wherein the 9a -halogen atom is fluorine chlorine or bromine and compounds of the formulae: <FORM:0878622/IV (b)/1> wherein R is a hydrocarbon radical containing 1-10 carbon atoms, wherein R1 is a hydroxy or keto and X is fluorine chlorine or bromine, and the process of treating 6-fluoro-9a -halo- 11b ,17a ,21- trihydroxy-4- pregnene-3,20-dione with an alkyl or aryl sulphonyl halide to obtain the corresponding 21-alkyl or aryl sulphonate of 6-fluoro-9a -halo-11b , 17a ,21-trihydroxy-4-pregnene-3,20-dione, treating the thus produced 21-ester with an alkal metal iodide to obtain 6-fluoro-9a -halo-21-iodo-11b ,17a - dihydroxy-4- pregnene- 3, 20-dione which is reduced, e.g. with zinc dust, sodium thiosulphate, sodium bisulphite and potassium bisulphite to obtain 6-fluoro-9a -halo-11b ,17a - dihydroxy-4- pregnene- 3,20-dione. If desired the 11-hydroxy group may be oxidised to obtain 6-fluoro-9a -halo-17a -hydroxy - 4 - pregnene-3,11,20-trione. Alternatively the removal of the 21-hydroxyl group may precede the introduction of the 9-halo group.  The process is applicable to both the 6a  and 6b  epimers the 6b -compound being epimerised to the 6a -compound by means of a mineral acid, e.g. hydrochloric acid.  Illustrative products of the invention are 6a ,9a -difluoro-21-desoxyhydrocortisone, 6a -fluoro-9a -chloro-21-desoxyhydrocortisone, 6a -fluoro-9a -bromo-21-desoxyhydrocortisone, 6a ,9a -difluoro-21-desoxycortisone, 6a -fluoro-9a -chloro-21-desoxycortisone, 6a -fluoro-9a - bromo-21-desoxycortisone, 6a ,9a -difluoro-11b ,17a ,21-tri-hydroxy-4-pregnene-3,20-dione 21-methanesulphonate and 6a ,9a -difluoro-11b ,17a -dihydroxy-21-iodo - 4 - pregnene-3,20-dione. Specification 850,833 is referred to.ALSO:Pharmaceutical compositions comprise a 6-fluoro-9a -halo-21-desoxyhydrocortisone or a 6-fluoro-9a -halo-21-desoxycortisone and a pharmaceutical diluent.  They are administered orally as pills, tablets, capsules, syrups and elixirs, in liquid forms for injectable products and topically as ointments, creams or lotions with or without coacting antibiotics, germicides and other materials. Specification 850,833 is referred to.
Patent GB-1357559-A (GB)
Title: Halogeno-6-hydroxy-pyridone-2compounds their manufacture and use
IPC: C07D213/69
Filed: 1971-08-12
Abstract: 1357559 Halogen hydroxy pyridones CIBAGEIGY AG 12 Aug 1971 [19 Aug 1970] 37895/71 Heading C2C [Also in Division C4] The invention comprises compounds of formula where one of the groups X is halogen and the other is hydrogen, -ON, -CO 2 R<SP>11</SP> (where R<SP>11</SP> is an alkyl or aryl radical) or CONH 2  and R and R<SP>1</SP> each independently represents a hydrogen atom or an optionally substituted alkyl, aryl or heterocyclic radical and also embraces the tautomeric forms of these compounds. The compounds may be produced by reacting a compound of the formula where X 1  is H, -CN, -CO 2 R<SP>11</SP> or -CONH 2  with a halogenating agent, e.g. sodium hypochlorite, sulphuryl chloride, chlorine or bromine under conditions such that when X 1  is H a mono halogeno derivative is obtained. When X 1  is -CN, CO 2 R<SP>11</SP> or CO 2 NH 2  it may be removed by saponification subsequent to the reaction with the halogenating agent. In the examples 1 methyl, ethyl or propyl 3 cyano or carbamoyl 4 methyl 6 hydroxy pyridone are reacted to form the 5 chloro or bromo derivative and theo substituent in the 3 position is removed. Many other reactants and products are mentioned. The products may be coupled with diazonium salts to form dyestuffs.
Patent GB-921394-A (GB)
Title: Thermal insulation
Inventor: FISHLOCK RONALD ARTHUR
IPC: E04B1/76
Filed: 1960-11-04
Abstract: 921,394. Insulating wall linings. ANCHOR INSULATING CO. Ltd. Nov. 3, 1961 [Nov. 4, 1960]; No. 38043/60. Class 20 (4). [Also in Group XXXIII] Thermal insulation is formed over the surface 1 of a chamber, e.g. a storage room in a building, by erecting a skin 10 of sheet material, e.g. plywood, spaced from the surface and attached thereto by means 11, filling the cavity 15 between the surface and skin with a foamed plastic which, upon setting, becomes rigid and adheres to the surface and the skin, removing the attaching means 11 and plugging the voids thereby left with foamed plastic. The attachment means comprises a bolt 20 (Fig. 3) having a screwdriver slot (not shown) at its outer end, a threaded inner portion 21 of reduced diameter which screws into a clip 26 to secure it to the rib 2, and a threaded outer portion 22 for the nuts 30, 31. When the foamed plastic has set, the bolt is unscrewed and removed, leaving the nut 30 embedded in the plastic. A recess 12 in the skin 10 is bridged as at 13 to provide a space 14 for equipment such as pipe-lines. If desired, an inner surface 40, e.g. of plywood, may be attached to the skin 10 by bolts 41.
Patent GB-1101028-A (GB)
Title: Tricyclic compounds
IPC: C07C2/42
Filed: 1965-09-07
Abstract: Tricyclic hydrocarbons of the general formula <FORM:1101028/C4-C5/1> wherein A is represented by a -CHR1- or by a -CHR1-CHR1-grouping, R1 is hydrogen or an alkyl radical having from 1 to 3 carbon atoms with the proviso that at least one of the R1's attached to ring 3 is hydrogen, may be prepared by the following methods represented by equations as shown; <FORM:1101028/C4-C5/2> in which R equals hydrogen or methyl. <FORM:1101028/C4-C5/3> <FORM:1101028/C4-C5/4> <FORM:1101028/C4-C5/5> <FORM:1101028/C4-C5/6> Examples are given of the preparation of 2,3,5,6,7,8, - hexahydro - 1,1- dimethyl - 1H - benz (f) indene; and 2,3,5,6,7,8, - hexahydro - 1,1,5,5,8,8, -hexamethyl - 1H - benz (f) indene.ALSO:Tricyclic compounds of a general formula <FORM:1101028/C2/1> wherein A is represented by a -CHR1- or by a -CHR1-CHR1- grouping, R1 is hydrogen or an alkyl radical having from 1 to 3 carbon atoms with the proviso that at least one of the R1's attached to ring 3 is hydrogen and wherein R2 is hydrogen, an alkyl radical having from 1 to 6 carbon atoms or a cycloalkyl radical comprises reacting a compound having the formula <FORM:1101028/C2/2> with an acylating agent yielding the moiety R2-CO- in the presence of a Lewis acid. Compounds claime per se are 2,3,5,6,7,8-hexahydro - 1, 1 - dimethyl - 1H - benz(f)-inden - 4 - yl methyl ketone; 1,1,5,5 - tetramethyl - s - hydrindacen - 4 - yl methyl ketone; 1,1,5,5 - tetramethyl - s - hydrindacen - 4 - yl cyclo - hexyl ketone; 1,1,5,5 - tetramethyl - s-hydrindacen - 4 - yl n - hexyl ketone; 1,1,2,3, 3,7,7 - heptamethyl - s - hydrindacen - 4 - yl methyl ketone; 1,1,3,3,7,7 - hexamethyl - s-hydrindacen-4-yl methyl ketone.
Patent GB-1123051-A (GB)
Title: Improvements in and relating to the production of blocks of asphalt and the like
Inventor: JONES PHILIP ANTHONY
IPC: C10C3/14
Filed: 1965-09-08
Abstract: 1,123,051. Stacking machines. AMALGAMATED ASPHALTE COMPANIES Ltd. 8 Sept., 1966 [8 Sept., 1965], No. 38360/65. Heading B8C. Blocks of asphalt are stacked on top of each other and are then compressed so that they stick together. As shown, asphalt blocks are fed singly by an endless conveyer between nip rollers 1, Fig. 1, and past a counter 10 so that they slide down a shoot 2, 5 into a stacking chamber 6, 7. Ledges 11a, Fig. 2, projected by pneumatic servos 12 in through the sides of the stacking chamber 6,7, receive the first asphalt slab, the succeeding blocks falling on its top. When the required number of blocks have been delivered, a pneumatic servo 14 is energized to raise a table 13 between the ledges 11a, which are then withdrawn outwards by the servos 12, and the table 13 is lowered to position the stacked blocks level with a transfer table 15. Next a transfer piston 16 pushes the stacked blocks horizontally off the table 13 on to the transfer table 15, and into a pressing station 18, Fig. 3. The stacked blocks are received on a table 19, which is lowered by a pneumatic servo 20 into a mould cavity 22. An hydraulic ram 21 is energized to engage the top of the stacked asphalt blocks, descending with the table 19, &c. into the mould cavity 22 and squeezing the blocks so that they stick together. The ram 21 then retracts upwards, and the servo 20 raises the compressed stack out of the mould cavity 22. A discharge plunger 23 operates to slide the compressed stack off the table 19 on to a final delivery station 24. During compression of the stacked blocks, another stack has been collected in the stacking chamber 6, 7. The operation of the various servos 12, &c. is connected by limit switches, &c. and the block counter 10. Should the machine malfunction, a servo 8, Fig. 1, is energized to turn the shoot 2 about a pivot 3 and direct the blocks down a reject shoot 9; simultaneously, an alarm is sounded. In a modification, the ledges 11a are replaced by pivoted catches (28, 28), Figs. 4, 5 (not shown), at one side of the stacking chamber (6), and the forward ends (27, 27) of a twopronged pneumatic plunger (25) at the other side. When a stack of blocks has been collected and lowered by the table (13), the pneumatic plunger (25) operates to slide the stack straight into the pressing station, passing through the stacking chamber.
Patent GB-917376-A (GB)
Title: Improvements in flame cutting machines
Inventor: BECHTLE RICHARD
IPC: B23K7/00
Filed: 1961-10-26
Abstract: 917,376. Electric copying machines. MESSER G.m.b.H., ADOLF. Oct. 26, 1961, No. 38412/61. Class 38 (6). [Also in Group XXII] Two photo-electric scanning heads 7, 8 follow two independent drawing or templates, and control, in an unspecified manner, two independent cutting torches 11, 12.
Patent GB-849716-A (GB)
Title: Apparatus for positioning neutron-absorbing material within a nuclear reactor
IPC: G21C7/10
Filed: 1958-12-01
Abstract: 849,716. Controlling nuclear reactors. UNITED STATES ATOMIC ENERGY COMMISSION. Dec. 1, 1958 [Jan. 21, 1958], No. 38625/58. Class 39(4). In a reactor safety and control member mechanism, a flat spring 76 is wound on a drum 34 driven by an electric motor through gears 68, 62, 58, 54 and an electromagnetic clutch. The spring carries a neutron absorbing plate 82 at its end, or absorbing strips distributed along its length. With the clutch engaged friction in the drive holds the drum still with the spring on it. If the clutch is disengaged the spring unwinds rapidly into a channel 86 set in the reactor, a spring 88 acting as a shock absorber. The drum carries a post 96 which engages, as the spring approaches the end of its travel, a dashpot plunger 104 through a swing- ing arm 98. Rollers 90 guide the spring. A gear train 108, 114, 116 drives the selsyn transmitter of a position indicator. An automatic safety trip arrangement is described. Specification 817,751 is referred to.
Patent GB-1291247-A (GB)
Title: Connecting coupling arrangement
IPC: A47G23/02
Filed: 1969-08-05
Abstract: 1291247 Cruets DART INDUSTRIES Inc 5 Aug 1969 [12 Aug 1968] 39209/69 Heading A4A [Also in Division E2] A condiment container 11 has a plug 23 releasably engageable with a socket 24 on a support 10 the plug having a base 18, inner wall 34 with a bead 35 and at least one slot, and an outer wall 32, the walls 34, 34 being engageable within outer and inner walls 24, 27, respectively of the socket so that an inclined surface 37 on the bead 35 engages against an inclined surface 30 on a bead 28 on the wall 27 to urge a shoulder 33 on the plug against the upper peripheral edge 25 of the socket wall 24, the container and support being made of plastics material and there preferably being three containers 11 on a support having a handle 14. Each container 11 has a removable closure 12 with a peripheral edge formed with an inverted U-shaped groove engageable with the container upper edge.
Patent GB-1560709-A (GB)
Title: Nitrotrifluoromethyl substituted diphenylamines their preparation and rodenticidal compositions
IPC: A01N37/34
Filed: 1976-09-22
Abstract: Novel diphenylamines of the formula <IMAGE> where the substituents are defined in claim 1, are prepared. These compounds are obtained by reacting an aniline which has the substituents R<1>-R<5> with a 2-halo-5-nitrobenzotrifluoride. The resulting compound is subsequently subjected to n-alkylation to introduce the substituent R. If necessary, halogen substituents are introduced by halogenation in the 2-, 4- and/or 6- position. The novel compounds are used as active substance in rodenticides.
Patent GB-1124687-A (GB)
Title: Improvements in or relating to closure means for fluid containers
IPC: B63B19/14
Filed: 1966-09-02
Abstract: 1,124,687. Hatch covers. ASSOCIATED CARGO GEAR A.B. 2 Sept., 1966 [16 Sept., 1965], No. 39281/66. Heading B7S. [Also in Divisions E1 and F2] A dome-shaped cover 4 adapted to seal against the coaming 1 of the hatch opening of a fluid cargo tank has two tie rods 7, 8 which are pivotally connected to the fitting 5B fixed to the conical top part of the cover 4 as well as respectively engaging a first fitting 13 and second fittings 16A, 16B at opposed sides of the coaming. Tie rod 7 consists of a bar 9 and a connecting piece 10 threaded to the bar and is honce adjustable in length. Tie rod 8 consists of two parts 8A, 8B interconnected by shaft 15 to form a Y-shaped member extending from the cover fitting 5B and opening towards the fittings 16A, 16B at the coaming.
Patent GB-1270136-A (GB)
Title: Polyphase alternating current frequency changer
Inventor: VILLIERS NICHOLAS CHARL DE
IPC: H02M5/27
Filed: 1969-08-07
Abstract: 1,270,136. Static frequency changers; control of A.C. motors. N. C. De V. ENSLIN. 7 Aug., 1969 [15 Aug., 1968], No. 39585/69. Headings H2F and H2J. A static frequency changer without an intermediate D.C. stage (e.g. for supplying a variable speed A.C. motor) comprises as shown, Figs. 3 and 7, a pair of output terminals A1 A2 and B1 B2 and C1 C2 for each load phase I, II, III and a plurality of power gates (e.g. SCRs or triacs) 16À1-16À6 connected to each output terminal and corresponding in number (three in present case RYB) to the number of supply phases. A selectively variable frequency control means controls the rate and sequence of triggering the power gates to modulate the incoming supply waveforms. Each power gate may comprise a triac or an anti-parallel pair of SCRs. Control circuits.-In Fig. 6 control frequency pulses are generated by a UJ oscillator 24À21 and monostable unit 24À22. The pulses C are distributed by a Ring counter 24À31 and combining gates 24À32 (e.g. AND, OR, NAND or NOR gates) via leads 22À2 to AND gate and trigger pulse generator units 18À1-18À6 (Fig. 3) together with synchronizing pulses S which prevent triggering of the power control gate SCR's out of their proper sequence. Interlock connections 28, between the RY and B phases trigger pulse AND gates 18À1 to 18À6 respectively control the AND gates so that the next SCR cannot be turned ON until the preceding one has extinguished. A power gate using a triac is illustrated in Fig. 10 (not shown) and power gates using SCRs are illustrated in Figs. 4 and 8 (not shown). Each load phase I, II, and III may be a phase winding of an induction or synchronous motor and the frequency changer is said to be capable of selectively varying the speed from standstill to twice the rated synchronous speed.
Patent GB-1400113-A (GB)
Title: Dielectric vacuum cleaner apparatus
IPC: H01L41/187
Filed: 1973-08-21
Abstract: 1400113 Dielectric ceramics TAIYO YUDEN KK and SONY CORP 21 Aug 1973 [20 Sept 1972] 39667/73 Heading C1J A sintered dielectric composition is composed in weight per cent of values inside the following limits PbTiO 3 , 2-31; SrTiO 3 , 35-83; CaTiO 3 , 2À8-20À1; Bi 2 O 3 , 3-19À1; TiO 2 , 0À5-18; TiO 2 /Bi 2 O 3  being from 0À2-2 to 1.
Patent GB-1270010-A (GB)
Title: A method of producing a flowable, granulated polyolefin wax
Inventor: JURY EGON
IPC: C08J3/12
Filed: 1969-08-12
Abstract: 1,270,010. Treating polyolefin wax. METALLGESELLSCHAFT A.G. 12 Aug., 1969 [13 Aug., 1968], No. 40247/69. Heading C3P. In a method of producing a flowable granular product from a polyolefin wax, particularly a polyethylene wax, freshly produced granular particles of the wax which are poorly- or non- flowable is set in motion by means of or in countercurrent to gas streams at ambient temperature in such a way that the particles of the granular material collide with one another and/or with confining or baffle surfaces under conditions such that substantially no disintegration or size reduction of the particles occurs. The poorly- or non-flowable granules may be prepared by atomizing a melt of the wax, e.g. by means of hot air under pressure, and the collisions may be effected by rotating brushes or by passing the material through a cyclone or blower. The material may be passed through a succession of cyclones or may be recycled through a single cyclone, e.g. four times. Apparatus for carrying out the method of the invention is described and illustrated.
Patent GB-1194538-A (GB)
Title: Electromagnets
Inventor: HARRIS PAUL ANTHONY
IPC: H02K33/10
Filed: 1966-09-09
Abstract: 1,194,538. Transistor oscillators. JOSEPH LUCAS (INDUSTRIES) Ltd. 10 Aug., 1967 [9 Sept., 1966], No. 40305/66. Heading H3T. [Also in Division H2] An electromagnet comprises a reciprocating plunger 21 slidably mounted in a housing 22 and urged by resilient means, e.g. a spring 23, towards one end thereof adjacent to but spaced from which end the housing contains a magnetic screen 24, two mutually coaxial windings 17, 14 within the housing and respectively between the screen and the said one and the other end of the housing and stated to be magnetically coupled together only when the plunger is in the housing first end region, and a transistor 13 whose collector and base are connected to respective windings 14, 17; such transistor and windings are connected in a circuit whereby when the latter are coupled the transistor conducts to permit energization of the winding 14 which moves the plunger against the spring action to break the magnetic coupling the transistor ceasing to conduct when the plunger has left the region whereupon the spring returns the plunger to recouple the windings and initiate a further cycle. A feed-back winding 16 surrounding the winding 14 is serially connected with a diode 15, a H.V. protective diode, as disclosed in Specification 1,018,785, may be connected across the winding 14, and an A.C. gain control capacitor and resistor may be connected between the transistor base and collector. Applicable to a road vehicle petrol pump, the plunger 21 may be the operative member and the entire unit including the electrical components mounted in a petrol tank.
Patent GB-1017046-A (GB)
Title: A process for the production of spinnable solutions of acrylonitrile polymers
IPC: C08F20/44
Filed: 1964-10-02
Abstract: Spinnable solutions of acrylonitrile polymers are produced by polymerizing monomers dissolved in aqueous nitric acid containing 55-68% by weight of HNO3 in the presence of a catalyst comprising peroxidic compounds and dicarbonyl compounds of heavy metals.  In the examples acrylonitrile is homopolymerized or copolymerized with methyl acrylate alone or with tercomonomers itaconic acid or sodium methallyl sulphonate.  Further monomers are specified.  Suitable peroxidic compounds include peroxydisulphuric acid and its ammonium and alkali metal salts, peroxymonosulphuric acid and acetyl peroxide. The dicarbonyl compounds are produced in situ from iron, copper or silver salts, e.g. nitrates and suitable organic dicarbonyl compounds such as acetyl acetone, benzoyl acetone, acetoacetanilide, dibenzoyl methane, barbituric acid, 5,5 - dimethyl-1,3-cyclohexanedione, resorcinol and phloroglucinol.
Patent GB-1112615-A (GB)
Title: An arrangement for measuring the proportion of a gaseous constituent in a mixture of gases
IPC: G01N7/04
Filed: 1965-09-22
Abstract: 1,112,615. Gas analysis. ANGA & VARME AKTIEBOLAG. Sept. 22, 1965 [Sept. 23, 1964; April 5, 1965], No.40352/65. Heading G1B. Apparatus for continuously measuring the proportion of a constituent e. g. carbon dioxide of a gaseous mixture comprises a reaction vessel 1 containing a reagent which absorbs the constituent e. g. potassium hydroxide, a supply pipe 2 to the vessel 1, provided with a throttle 6 and connections to a housing 8 divided by a membrane 9 into two chambers so as to control a valve 15, 16 so that the gaseous mixture is supplied to the vessel 1 at a constant rate, an outlet throttling nozzle 3 from the vessel 1 adapted to maintain a pressure above atmospheric therein, and a pressure gauge 5 connected to the vessel 1, and provided with a scale directly indicating the percentage of the desired constituent of the gaseous mixture. To avoid effects due to temperature variations in the gaseous mixture supply, the pipe 2 may be made to pass through the vessel 1 and may be coiled therein to act as a heat exchanger.