February 23, 1917. THE COLLIERY GUARDIAN. 387 "o 02 Maximum mark s• obtainable on written paper. Maximum number obtain- able on oral examination. Total. _ A First class. Second class. t First class. Second class. First class. Second class. 1 ... 250 . ... 300 ... 100 ... 180 ... 350 ... 480 2 ... 200 . ... 300 ... 80 ... 180 ... 280 ... 480 3 ... 130 , ... 100 ... 52 ... 60 ... 182 ... 160 4 ... 150 . .. 100 ... 60 ... 60 ... 210 ... 160 h ... 140 . ... 100 ... 56 ... 60 ... 196 ... 160 6 ... 130 .. 100 ... 52 ... 60 ... 182 ... 160 Total.. 1,400 ...1,600 The candidate may within the period of three years as aforesaid be re-admitted to sit for examination in any group or groups in which he fails to qualify. 3. If the candidate satisfies the Board that he is dis- abled from executing mechanical drawing or preparing plans, the Board may dispense with the production of the plan and levelling referred to in paragraph 4 (a) (v.) of the said rules as amended by the rules made by the Board on September 9, 1913, and may direct that an allowance of marks shall be made to him in respect of any drawing or plan which the candidate would have been required to execute in answering any question in a written examina- tion ; provided that the candidate satisfies the examiners in his oral examination that he possesses the knowledge necessary to comprehend and to make any drawing or plan or levelling which he would otherwise have been required to make. 4. If the candidate satisfies the Board that he is dis- abled from writing or can only write with difficulty, the Board may substitute an oral examination for the written examination, provided that the standard of examination is not thereby lowered. TRADE AND THE WAR. The new imposts in the German Budget for 1917 include an ad valorem tax on coal output. Messrs. Be ver, Dorling and Company Limited, engineers, Bowling Iron Works, Bradford, have been appointed sole licensees for the Capell patent fans. The Government of India has exempted sulphate of ammonia from the import duty leviable under item 93 of the amended Indian Tariff Act, 1894. A serious condition of affairs has arisen at different American ports owing to the number of ships which have not sailed because of the German blockade policy. Quays and railway terminals are congested and choked with freight. An increasing output of brass castings is included in the business of Messrs. Lancaster and Tenge Limited, engi- neers, iron and brass founders, Lancaster Works, Pendleton, Manchester. We .are informed that the present average output of brass castings is 10 tons per month. The Board of Trade has ordered the winding up (under the Trading with the Enemy Amendment Act) of the Coal "Distillation Company, manufacturers of coke ovens and by-product plants, Middlesbrough. The controller is Mr. G. B. Nancarrow, Royal Exchange, Middlesbrough. The Public Trustee invites tenders by April 2 for the pur- chase of the whole or any part of 119,660 shares of £5 each, fully paid, in Siemens Brothers and Company Limited, vested in him as custodian, by an Order made by the Board of Trade in pursuance of the Trading with the Enemy Amendment Act, 1916. The annual return of exports from Sheffield to the United States, issued by the United States Consul in Sheffield, shows that during 1916 coal tar products rose from 7,904 to 17,243 dols. In exports to the Philippine Islands, an increase of 11,569 dols., or more than 150 per cent., in coal tar products is reported. The Minister of Munitions has made an Order under the Defence of the Realm Acts and the Munitions Acts, requir- ing that all persons shall in the first seven days of each month, beginning in March, send in to the Director of Materials, A.M.2 (H), Hotel Victoria, Northumberland- avenue, London, S.W., monthly returns of their stock of aluminium and all transactions relating to same. According to a statement by Mr. Bonar Law this week, the committee appointed to report regarding the liquidation of liabilities between British 'and enemy persons consists of Sir H. Babington Smith (chairman), the Right Hon. D. Maclean, M.P., the Hon. M. Macnaghten, Sir Algernon Eirth, Sir W. Blender, Messrs. C. J. B. Hurst (Foreign Office), Brien Cokayne (Bank of England), W. Leaf, C. J. Steward (Public Trustee), J. J. Wills (Board of Trade), and H. Mead Taylor (secretary), Gwydyr House, Board of Trade. Owing to the continually increasing cost of raw materials, the manufacturers of Ferodo fabrics have been compelled to advance the. prices of these fabrics 15 per cent., so that list prices 'are now plus 25 per cent, instead of plus 10 per cent, as hitherto. This increase came into operation on January 1 last, and it is only due to the fact that the makers held large stocks of raw materials, of which they determined to 'give their customers the advantage, that prices have been maintained at their previous level for so long a period. The well-known quality of Ferodo fabrics is fully maintained, and engineers, motorists, and other users will find that there are no friction surfaces so efficient, reliable, and economical as Ferodo linings. Should any difficulty be experienced in obtaining supplies, a post card should be addressed to the makers, the Herbert Frood Company Limited, Chapel-en-le- Frith, Derbyshire. Sir Robert Hadfield has accepted the presidency of the Society of British Gas Industries, in succession to Mr. Duke, K.C., M.P. The Board of Trade has assumed control of the canal system, including all buildings, barges, machinery, and plant used in working canals. The Board has power to make exceptions. The estate of Mr. F. W. Harris, one of the chief pro- moters of the Deep Navigation Company, and after whom Treharris was named, has been proved of the value of .£150,000, “ so far as can be at present ascertained.” There is a bequest of £500 to the Coal Trade Benevolent Society. CURRENT SCIENCE Thermal Decomposition of Low-Temperature Coal Tar. Mr. D. T. Jones (Journal of the Society of Chemical' Industry) summarises the question of the thermal decomposition of low-temperature coal tar las follows :— (1) Ordiniary coal tar is formed from coal at high temperatures, chiefly as the result of the decomposition of a tar previously formed at low temperatures. (2) The mechanism of this process consists essen- tially in the decomposition of the naphthenes, paraffins, and unsaturated hydrocarbons present in the low tem- perature tar to form olefines of varying carbon content, which condense at higher temperatures to aromatic substances. (3) The higher (gaseous) olefines are at a maximum at 550degs. Cent., the curve descending to a minimum at 750deigs. Cent., when they virtually disappear. Their disappearance at 750degs. Cent, synchronises with the appearance of naphthallene, and immediately precedes a rapid increase in the evolution of hydrogen. (4) Hydrogen is formed at middle temperatures, chiefly as the result of the decomposition of naphthenes. The increase at higher temperatures must probably be attributed to the union of aromatic molecules and to intramolecular ring closing. (5) Phenols are primary products of coal distillation. (6) Benzene and its homologues are chiefly formed as the result of olefinic condensation. To some extent they are secondary products of coal distillation, having been formed by the thermal dehydrogenation of the corre- sponding naphthenes. (7) Acetylene plays an insignificant part in coal tar formation. A New Method in Gas Analysis. K. A. Hofmann and O. Schneider (Gas World) have recently compared the' activities of platinum, rhodium, palladium, osmium, and other noble metals, in relation to hydrogen, carbonic oxide., methane, and ethylene. Shaking up solutions of sodium chlorate and sodium bicarbonate containing salts of these metals along with different gases, they found platinum to be the best pro- moter of activity as regards hydrogen, osmium as regards carbonic oxide, while methane was hardly affected by the presence of ’any of the metals. In order to make the action upon hydrogen rapid enough for purposes of gas analysis, it was found necessary ibo com- bine palladium, osmium, and a large surface of platinum. This last was provided by burning off a porous clay tube dipped in a 5 per cent, solution of platiinic chloride. These porous clay tubes were' put, platinised ends up, in a Hempel pipette with a solution of 35 grms. sodium chlorate, 5 sodium bicarbonate, 0*05 palladium, chloride, and 0’02 osmium dioxide in 250 c.c. water. By this means the hydrogen was estimated in presence of nitrogen or methane more readily than by the usual combustion methodis. The speed of oxidation of the hydrogen was greater the greater the exposed area of platinised clay surface; and without shaking 60 c.c. of hydrogen could be removed in 10 minutes. The gas to be examined must be free from ammonia, sulphur compounds, and phosphorus compounds. Methane is not affected even in the presence of nitrogen or air. Oxygen is not absorbed unless hydrogen' be present. Blasting with Quicklime. The expansion of quicklime when wet develops an enormous force that acts slowly and almost irresistibly, and has long invited use for mechanical purposes. A large amount of time and money has been spent trying to adapt it to raising heavy weights, as in under-pinning buildings and other structures; and more successful efforts have been noted in a recent issue of Rock Products that describes its efficient use in breaking up heavy brick masonry. A number of 12 ft. by 20 ft. piers, 12 ft. high, were located between similar founda- tion piers for engines in operation, and it was necessary to remove them without injuring the machinery. Blast- ing was therefore inadmissible, and hand-cutting and breaking too slow and expensive. The work was accom- plished by drilling 3 in. vertical holes 3 ft. deep and 3 ft. apart in both directions over the entire areas of the piers, and filling them within 6 in. of the top with fresh slaked lime in pieces Jin. to 1J in. wide. As soon as the lime was thoroughly wet, the tops of the holes were filled with brick drilling well tamped, and in about 10 minutes cracks started in every direction, and the entire top of the foundation pier was broken into 3 ft. cubes. Careful work was necessary, since there was some danger of the tamping being blown from the tops of the holfes. Potash from the Blast Furnace. Mr. R. J. Wysor (Bulletin, American Institute of Mining Engineers) describes the method pursued, at the works of the Bethlehem Steel Company, for recovering potash from blast furnaces. The iron ore used contains about 0’3 per cent, of potash and 0’7 of soda; in the manganese ore the potash exceeds 1 per cent., but the coke and the lime and magnesia of the flux reduce the averages in the total furnace charge to 0’28 per cent, of potash and 0-63 per cent, of soda. The slag contains 0*39 per cent, of potash and 0*56 of soda, but in the crevices of slag dumps yellow-white salt deposits are formed containing up to 18 per cent, of potash, only half as much soda, a great deal of lime and sulphur, but no magnesia. Washing the blast furnace gas from the dust catches leaves 20 per cent, of potash and 5 per cent, of soda in the gas, the fumes being too fine to be absorbed by the coarse washing spray. The dust accu- mulating in two or three months in the gas mains lead- ing from the washers contains 44 per cent, of potash. The fine, light-coloured dust collecting in the second and third passes of the stoves is the chief material for potash extraction; the passes are cleaned every three or four months. A similar dust accumulates in the boiler AND TECHNOLOGY. house, and contains from 5 to 20 per cent, of potash soluble in water. Extraction experiments at Bethlehem (extending over a period of 14 months) with the dust from the stoves and boilers serving four 500-ton fur- naces, showed that the composition of -this dust (over 1,000 tons) varied greatly. It contained about 20 per cent, of silica, 11 of alumina, 12 of lime, 9 of magnesia, 7 of sulphuric acid, and 4 of chlorine, but neither ammonia nor cyanogen compounds, these being destroyed by the roasting the dust had undergone. From the results obtained, it appears that of the total potash entering the furnace, 20 per cent, was lost in the slag, 2 per cent, lost in direct fumes from the furnace, 3-9 per cent, escaped with the gas, 2*7 per cent, was recovered in the dust catchers, 60 per cent, lost in the primary washers, 2 per cent, lost in the secondary washers, 1-3 per cent, lost in stove and boiler passes, and .11 per cent, lost in stack gases; the losses of soda in the primary washers were even greater than those of potash. The amounts of potash and of soda actually recovered were 1-3 and 0-3 per cent, of the totals. Moreover, part of the gas, directly from the dust catchers, was treated, in electric precipitators, by the Cottrell process, and about 10 per cent, of potash was found in this dust. Removal of Rust from Iron Plates. As a result of experiments recently carried out at the Consolidated Gold Fields Laboratory, Mr. F. W. Watson (Journal of the Chemical, Metallurgical and Mining Society of South Africa) reports that an easy, cheap, and effective method of removing iron oxide from cor- roded and pitted iron plates has been evolved. Previous practice on the Rand has been to remove this mechani- cally, either with hammers, chisels, or a sand blast. Whilst largely efficient, each of these methods is liable to leave traces or nodules of rust, especially at the bottom of the pitting, and these nodules prevent the covering of paint adhering to the iron, and form nuclei for further corrosion. The method evolved consists in applying to the surface of the iron a mixture of finely crushed sodium bisul- phate and common salt, in the proportion of two parts of the former to one of the latter. This mixture is prepared, then wetted (just sufficiently to be cohesive) and applied to the iron plate. If time be no object, the moist mixture can be left till the plate is clean, but the action is much more rapid if the mixture is scraped off every two or three hours and the iron scrubbed thoroughly with a wire brush, applying waiter at the same time. The treatment is repeated till the plate is clean. Usually 24 hours is sufficient for a badly cor- roded plate. The liberation of hydrochloric acid takes place slowly, and its action on the metallic iron appears to be slight. When the plate is thoroughly clean, it is washed well, finally with an alkaline solution, and dried quickly. A coating of paraffin oil is at once applied to protect the surface against atmospheric action. The metal is then ready for application of paint or other protective covering. MINING INDUSTRY AND MILITARY SERVICE. Newcastle tribunal has conditionally exempted the head of a coal and coke exporting business, aged 26, single, and passed for 0 3. His chief assistant, passed for Bl, has been given two months’ final exemption. The Lanchester tribunal has granted conditional exemp- tion to two woodmen, 28 and 26 years respectively, both single, who are engaged in cutting timber to keep the pits going. The claim was supported by the Home-Grown Timber Committee, Westminster, who urged that the supply of English timber for mining purposes must not be diminished. These two men cut down 200,000 ft. of timber during last year. The military representative said that he must appeal in the case of one man who had been passed for general service. By 'agreement with the Army Council, the Board of Educa- tion arranged for the exemption of certain teachers, students, and officials of educational establishments coming under their supervision whom they considered should not, for the time, be taken from their civil employment. All exemptions of this kind granted to men in medical category A, or to men under 31 years of age in medical category B L have been withdrawn. Men not examined by 'a medical board must be regarded as in category A. The Seaham Harbour tribunal has renewed the exemption of a colliery bill clerk, passed C3, on the understanding that he joins the V.T.C., and that if he cannot attend the drills, he is to produce a certificate from his manager as to the reasons. —’ The South Hetton Coal Company has obtained temporary exemption, for six months, for a horse driver, employed on Seaham staiths in the moving and shunting of wagons in connection with coal shipping, always provided that no substitute can be found, and that the man joins the V.T.C.—Of three trimmers employed by the Seaham Harbour Dock Company, the youngest has been sent forward, and in the case of the other two it hais been decided that they shall remain where, they are until efficient substitutes can be found. They also are ordered to join the V.T.C. The tribunal further aisked Mr. Black, the docks company’s engi- neer, to do all he could to, release general service men and take on others in lower grades, and Mr. Black said he was endeavouring to do thait at present. The directors of the South Metropolitan Gas Works are urging all their customers to use gas coke instead of coal. The arrangements for holding a meeting of the Coke Oven Managers’ Association (Midland branch) on February 24 have been cancelled. Siemens Brothers Dynamo Works Limited have removed from Caxton House, Westminster, to Palace Place Man- sions, Kensington-court, London. Mr. R. J. Browne has been appointed a temporary inspector of mines and temporary inspector of factories and workshops (unpaid).