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Vol. 21, No. 8
centration of lead tetraethyl was increased. Tanaka and By analyzing samples of gas withdrawn from an engine Nagai (17) noted that small amounts of selenium diethyl, lead cylinder a t various points in the explosion period by means of tetraethyl, pyridine, or aromatic amines raised the spontaneous a special quick-acting, water-cooled sampling valve, Lovell ignition temperatures of alcohols, but had little or no effect on and Coleman with Boyd (IO) showed "that when the engine those of methyl cyclohexane and ether. Later ( 7 , 21) com- knocks, whether the detonation is caused by the presence of pounds which have good antiknock effects were observed to kerosene in the gasoline or by a chemical knock inducer (isoincrease the spontaneous ignition temperatures determined propyl nitrite), the gasoline burns a t a rate more rapid than for a number of fuels by means of a modified Moore meter. normal. It may be seen, also, that the presence of tetraethyl EFFECT OF KNOCK SUPPRESSORS AND KNOCK INDUCERS ON lead in the knocking combustion brings the rate of burning OXIDATION OF DIFFERENT FUELS-Callendar ( I ) found that back to normal, within the probable limits of error." Upon the oxidation of hexane-air mixtures during their passage the basis of similar investigations, Egerton and Gates (6) through glass tubes heated a t 35C-500" C. was less in the reported that doped fuel is much less easily oxidized than presence than in the absence of lead tetraethyl, iron carbonyl, ordinary fuel during the compression stroke in a variable or nickel carbonyl. Experiments by Lewis (9) revealed the compression engine. fact that isopentane, heated, a t temperatures below its igniL i t e r a t u r e Cited tion point, with oxygen in glass bulbs, was made more resista n t to oxidation by the addition of 1 per cent of lead tetra(1) Bennett and Mardles, J. Chem. SOL.,1927,3155. ethyl. Layng and Youker (8) observed that the slow oxida(2) Boord and Schaad, Oil Gus J.,23, No. 16A, 78 (1924). tion of heptane in the gas phase a t 160' C. was inhibited or (3) Butkov, Erddl Teer, 4, 162 (1928). prevented by 1 per cent of ethyl fluid. I n similar experi(4) Callendar, Engineering, 123, 182 (1927). ments the oxidation of heptane was accelerated by 1 per cent (5) Dumanois and Mondain-Monval, A n n . ofice nul. comb. liquides, 3, 761 (1928). of butyl nitrite. Bennett and Mardles ( I , 1%') have likewise (6) Egerton and Gates, J . I n s f . Pefroleum Tech., 13,264, 277 (1927). reported that lead tetraethyl and nickel carbonyl increase (7) Egerton and Gates, Ibid., 13, 244 (1927). the ignition temperatures and inhibit the low temperature ( 8 ) Layng and Youker, IND.END.CHEX.,20, 1049 (1928). oxidations of hydrocarbons and other fuels. (9) Lewis, J. Chem. Soc., 1927, 1563. Butkov (S) found that n-heptane in a bomb a t 230" C. (10) Lovell and Coleman with Boyd, IND.ENG.CHEM.,19,376 (1927). under a pressure of 3 atmospheres of oxygen yielded carbon (11) Mack, Boord, and Barham, Ibid., 16,963 (1923). dioxide six times more rapidly than did the same fuel to which (12) Mardles, J . Chem. Soc., 1928,872. ENG.CHEX., 21, 544 (1929). (13) Masson and Hamilton, IND. 2 per cent of aniline had been added. Dumanois and Won- (14) Ormandy and Craven, J . Inst. Pelroleum Tech., 9, 33 (1923). dain-Monval (5) made somewhat similar experiments on (15) Ormandy and Craven, Ibid., 10, 335 (1924). pentane confined in a rotating, cylindrical steel bomb under (16) Stromeyer, Mem. Proc. Manchesler Lit. Phil. SOL.,46, No. 8 , 1 (1902); J . Chem. SOL.,82, ii, 251 (1902). an initial air pressure of 5.3 kg. above atmospheric and heated gradually from 20" to 300" C. Under these conditions the (17) Tanaka and Nagai, J . SOL.Chem. Ind. ( J a p a n ) , 29, NO.5, 68B, 61B (1926). oxidation of pentane-air mixtures richer than that for complete (18) Thompson, IND. ENG.CHEM.,21, 134 (1929). combustion was inhibited by the presence of 0.11 per cent of (19) Thornton, Proc. Roy. S O L .(London), A90, 279 (1914). lead tetraethyl. This small quantity of the knock suppressor (20) Thornton, Phil. Mag., 38,613 (1919). increased the spontaneous ignition temperature by about 10" C. (21) Weerman, J. Inst. Petroleum Tech., 13, 300 (1927).
Safety in the Manufacture of Sulfuric Acid by the Contact Process' Stanley H. Kershaw INDUSTRIAL
I
DIVISION,N A T I O N 4 L SAFETY
N IKDUSTRY an efficient process is often a relatively
safe one. Good equipment and proper maintenance place i t in even a more favorable position from a safety standpoint. This is true in a large measure in the case of the contact process of manufacturing sulfuric acid. The principal hazards of this process are: (1) Exposure of men to sulfur dioxides, sulfuric acid fumes, arsenic, selenium, and sulfur dust. (2) Possibility of sulfur dust explosions (preventable by wetting down while handling). (3) Possibility of undermining sulfur stock piles with subsequent cave-ins on men. (4) Ordinary machinery hazards in sulfur burner and blower rooms and where belts, pulleys, and gears are used to transmit power t o pumps. ( 5 ) Drips and sprays of acid from leaks in pipe lines and tanks. (6) Acid flowing from broken gage glasses. (7) Exposure t o fumes and acid when men are required to work inside tanks, towers, and other apparatus. (8) Hazards incident t o the handling of heavy pieces of equipment when making repairs. 1
Received M a y 1, 1929.
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It is important that the men wear gas masks whenever exposed to concentrated sulfur dioxide and sulfuric acid fumes; also arsenic and selenium of only mild concentration as when treating the contact mass for the purpose of reviving. Respirators and goggles of good design will afford ample protection against sulfur dust. Reasonable care in shoveling sulfur from the piles will help t o prevent men being injured by cave-ins. However, when working from large piles close supervision is necessary. There is ample information available from many different sources on methods of safeguarding all ordinary machinery hazards. Drips and sprays of acid from leaks in pipe lines and tanks are preventable by good original installation work, careful supervision of operations, and avoidance of makeshift repair work. Only the best acid-resisting packing material in joints and valve glands and plenty of acid-resisting paint should be used to prevent external corrosion. Gage glasses should be used in acid tanks only if absolutely necessary. They should be regarded as extra hazardous and the best possible precaution taken against their breakage. They should be amply protected with stout guards. Water
August', 1929
IhTDUSTRIAL A.1-D EiYGIATEERING CHEXISTRY
showers (commonly called safety showers) should be provided in ample number to enable a man splashed with acid to reach one conveniently from any position adjacent to the apparatus. They should be placed not more than 50 feet from any operating position in which a man might be splashed or sprayed with acid, and the man should not have to make more than one right-angle turn in his effort to reach one. The showers should be equipped with quick-opening valves and the sizes of the heads and riser pipes should be sufficient to deluge one with water. Work inside tanks and apparatus requires the utmost precaution for safety. 'The tanks or apparatus should be thoroughly freed of all acid and fumes by thorough and repeated washing and steaming, winding up by filling with a weak soda solution and allowing i t to stand long enough to neutralize all acid. All mud should be removed, became when stirred up i t liberates fumes. It pays to have the men who enter protect themselves with gas masks and safety belts. The belts are used with life lines attached so that quick rescue can be made from outside the tanks or apparatus if anything goes wrong. Attendants should always be stationed a t the tank manholes while men are inside. Each acid pipe line leading to the tank should have a section removed and the
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end blanked off so there can be no possibility of acid entering while the men are a t work. Ample provision should be made for the handling of heavy parts in time of repairs. Much can be done to facilitate this in the original design of the buildings by providing anchorage of sufficient strength for hoists and by including large doorways and floor openings. The latter should be protected with railings and toe-boards. I n general, it is well to make all parts of the apparatus easily accessible by the provision of good permanent walkways and stairways. Stairways should be provided in preference to ladders in so far as possible. It is always good from a safety standpoint to place acid pipe-line valves not more than 18 inches above floor levels, so that the operator can keep his face well away from them. However, all important passagemys should be kept clear of pipes which would form stumbling hazards. Floors should be of acid-resisting material and sloped to drain well to sewers or pumps. Ample water hose and outlets should be available for washing away spills of acid. Adequate ventilation is always important in buildings housing acid processes and is usually obtained by roof monitors supplemented with wall openings a t the ground level to provide the necessary circulation of air.
Effect of Nitrate Oxygen upon Tannery Effluent' Edwin R. Theis and John A. Lutz WILLIAM H CHAXDLERC H ~ M I C ALABORATORIES, L LEHIGHUNIVERSITY, BETHLEHEM, P A
NE of the most imporThe reduction of nitrate in the presence of oxidizable presence of n i t r a t e s . Butant processes in the organic material has been studied and the following chanan and Fulmer further manufacture of leather facts have been noted: (a)the amount and composition point out that the oxygen is the proper soaking of the of the gas produced during the reduction; ( b ) the secured through reduction of hides or skins, and for this amount of reduction taking place under various condinitrates and nitrites is availtions; ( c ) the gas pressure attained during the reducable to the organism quite as reason l a r g e a m o u n t s of tannery soak water are passed tion of the nitrate. readily as atmospheric oxyIt is shown that large amounts of nitrogen are libergen. The reduction of nito rivers and streams. Hides and skins are generally soaked ated through the reduction of nitrate by bacterial actrate with subsequent oxidafrom 24 to 48 hours, and it is tion and it is pointed out that this nitrogen may be tion of sulfur liberates energy usually found upon examinaderived from several sources. During the early stages f o r b a c t e r i a l u s e . Extion that the resulting soak of the reduction considerable carbon dioxide is properiments have shown that miter contains no dissolved duced, indicating that the carbonaceous material is tannery soak water is very oxygen-in bacteriological acted upon most readily. At a later period it appears s t r o n g l y reducing in charparlance, the water is strictly that the sulfur compounds are oxidized by the nitrate. acter and acts upon sodium anaerobic. The effluent from nitrate with great avidity, a 48-hour soak may contain upward of 300 million bacteria giving a variety of products. When nitrate is added t o per milliliter of soak water, and for this reason the oxygen these lvaters, the folloming reactions may be visualized: requirement of the wvster is extremely high. RIany workers have studied the effect of nitrate oxygen upon sewage in (N01)2H' 2 e ---f (NOz) Hz0 NOz 2 H + Z E +NO HzO general, but apparently little has been done with regard to 250 4HC 46 +J S z 2H20 tannery effluent. IS0 f 6 H + 5, +NH3 + H2O Urbain (4)has pointed out that it is necessary for anaerobic NH3 HNOz +XHaNOz +NO 2H2O conditions to exist before nitrate oxygen can be utilized by bacteria. The present writers have found this contention I n determining the biochemical oxygen demand by the nito be in accordance with their experimental work. However, trate method it is usual to estimate the residual nitrate and in utilizing tannery soak water, the effluent is practically free nitrite in the incubated solution. The writers believe that from dissolved oxygen and is consequently anaerobic. Many this leads to erroneous interpretation, because it appears that bacteria have been foiind which are capable of rtbducing nitrates to nitrites. Buchanan and Fulmer ( I ) point out more of the nitrogen cycle should be estimated. Theis and that most of these barteria are strictly aerobes except when AIchIillen (5) showed that on treating tannery soak water able to reduce nitrates and nitrites. These bacteria are pro- with standard solutions of sodium nitrate large amounts of the teolytic and unable to act upon carbohydrates except in the nitrate were consumed. Table I gives a summary of the data. This table shows that comparatively large amounts of nitrate 1 Received April 6, 1929 Presented before t h e Division of Water, are consumed but only small amounts accounted for in the Sewage, and Sanitation Chemistry a t t h e 77th Meeting of t h e Amerlcan Chemical Society, Columbus, Ohio, April 29 t o M a y 3, 1929. usual analysis. Buswell (8)points out the conflicting evi-
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