pigment produces a dull, serrated film, which flakes rcnrlily and is wort,liless for ordinary use. Such variations in the hehavior of t.he two pigments are frequentiy encountered.
Finurr 6 X I S 0
Thus each defective vaniish, made according to its own forinula from a given hatch of raw material, which may difer widely from otlier lots of the same material, presents its own problem in determining a remedy. It is common experience in varnish mixing t o find that t.wo batches of varnish, made up according to tlic same formula, differ markedly in the quality of the product secured, simply because of minute variations in the physical niid chemical properties of the ingredients. It is impossible to offer a universnl remedy for the various defects. It is usiially difiiault t,o trace any one defect to the Foiidan~ental mise, Immise of tlie inability to obtain a ~.oiiipIeteliist,ory of the methods of preparation of all the ingredieiits. Sinall varitttions in the methods of preparation may prodwe radieal changes in wcttabilities, adsorptive tendencies, ctc. As a rule, a nricrosropie cxaiirinatimi of a drying film of :my varnish is a dependable guide in the determination of its qualitips. On siich examinations and observations these papers have bccn largely based. The writers have eonsidered principally the fuiictions of the volatile and of the vortex action wliioh it produces. A thorough eomprrhension of the rdation of vortex act,ion t,o tlie drying of varnish filnis seem to be fiindaniental to an investigat.ion of the varions defects encountered.
Hazards in the Handling and Transportation of Acid' The Safety Factor By Maurice F. Crass Ttia G X A ~ ~ SCCnL&~m c Co ~ ~, CLBY~LAIID. Omo
LL lines of industry have their package and transportation problems. The difficulties involved are intonsified where the products constitute a hazard t o handlers and merchandise in case of hrcnkage or rupture of the packages. The ignora.nce or cnrel~!ss~rcsseoinrnonly displayed in t.he handling of acid is iri nu sinall dcgree rcspimilile for the safety rating given acid contaiiicrs, whidi mting wouiil be grently iinproved if all x h o 11andIe these p;L(:kages used lnethods best calculat.ed to give the maxiiriurn of safety arid efficiency. Malpractice in this resper:t is not confined esclusivcly t,o tlie t,ransportation and consuming agcnries. Rererit surveys hare slioviii tlie necessity for a close coiiperativc policy bch 11 pnidnccrs and iiscrs of acid. Acids most coinmonly used, such as sulfuric (including dcotrolyte or battery aoid), muriatic, slid nitric are rated liy the Bureau of 13xplosives under the "Dangerous Article" class and are therefore accepted for transportation only (Interstate and Intrastate Commerce) when in compIianue with the 1nterst.ate Commerce Commission's regulations. Tlie policy followed by the Bureau of Explosives in drafting of committee surveys in which the specifiratii,ns-that industry has opportunity t.o make suggestions and corrections--has improved conditions to such a degree that t.he proportionate losses incident t o transportation are less than for many products not included in tlie "Dangerous Article" class. The cooperation of producers, transportation agencies, and consumers must continue if best possible results in reducing losses and safety in handling are to be attained. Packages used for the transportation of acid8 musk conibine carrying strength, adaptability, ease of filling and dis-
A
1
Received May 14, 1925.
charge, with a type of construction best suited to withstaxid the action of the acid. A container that will serve for one acid may not be suitable for another. For this reason acid containers are syreeinlly coiistructrd for the service intended. This is one of the chief reasoxis why the regulations are so specific. The type of construction is usually expcrrsive, both in first mst and maintenance, and only possible to maintain because of tlic returnable feature which amortizes the cost over a tolinage otlierwise prohibitive. Generally speaking, the following materials are considered most elliaient carrying agents-erosion, conta.inination of product, slid st,rcrrgth of construction considered fur the finished i'ontaiocr: S u ~ a u n i cAcm
IiyDeocI%omc Aciu
h7marc Acru
M i x s o Acru ACETIC ACID
(including glacirll
Boxed ghss caiboyr: See I. C. C. Spec. 1 Steel drums of 55- aud 1IU g ' ~ l l o ncapacity: Src I. C . C. Spec. 5.A Steel tank ears: See American llailnay Assor. m d 1. c. c. regu1iltions ,Boxed EIBSE earboys rianrporistion tanks: wood stave tresied UI rubber limed. Sfecl shell, kubbn lined Sfeel drums: soft rubber lined Boxed &as carboys with incombustible packing: See I. c. c. Spec, 1 Special steel drums: used only loi acid cooiaiiiiny rerfr,in malinllllii l1niitatiD"S on IDWC, oxides of nitro~en hgdiochioric, and ruifmic with P minimum &r cent of HNOi Stre1 drums and steel.tank ears. aame regulhtionr as sp14y to sulfuric acid l h n r z m t s t i o n tanks: wood stave construction, paras" tiented
Harrlwoid barreis: oaraIfin~8 Boxed lass criboye Note-Glass carboys m e best suited for glacinl, because ot danger of discoloration of Product ~~~
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when shipped iu baiiclr
AQUAAMMONII
C. P. Arauliia
Steel drums: m-11 seasoned Steel tank cars: well Seasoned I3oxed g l a s ~carboys Steel drums: well seasoned Boxed glass carboys
5 and I pint glass-stoppered bottles in pzckcd case,
October, 1925
INDUS'TEIAI, A N D ENG[NEERING CNE.WIASTRY
A brief historical review of the developirient of a few chemical packages will give a better underst.aiiding of the necessity for the restrictions imposed hy the American Railway Bssociation and Interstate Commerce Commission. Carboys
The well-conditioned carboy cannot he conaidert?d as a fragile container, although therc are definite limits t o its shock-resisting strength. A broken carboy eiiniute means possible damage to merchandise, as well as danger t o workmen wlio may not be inforincd as to the proper nietliod of dealing with such leakage. The insistence, therefore, has been for a stronger, better-conditioned carboy and regulations that would eliminate the unfit. A study of the problem was undertaken by a corrunittee of representatives from the Il.lanufactiiring Chemists' Association of the United States and the Bureau of Explosives. The preliminary siirvcy disclosed ample cause for complaints made by the railroads, who had sulrcred undue losses from broken niid defective carboys. Itegulations governing sliockresisting streiigtli, standardization of construction, and maintenance were so general and unscientific that very little, if any, Inmefit was dcrired therefrorn. in dropping and aide strain tests were prescribed, but the inctliods were in inariy cases so crude that the tests were of little value. The coiiimittee, therefore, devoted much time, pains, and rnoney in determining: (1) a maclrine that would give an approximately perfect swing strain test; ( 2 ) reasonable strain dest reqoirements; and (3) reguliitkins gnvwning conditioning of carboys, perfecting of seals, etc. With a standardized swing testing maaliine, it became necessary to determine the minimiirn shock to which carboys should lie subjected. This was a difficult matber, for it was necessary to considcr (1) tlie elimination nf a large nurohcr of curhnys then in circulation, whicli were not equal in strength to otlier better constructed or better conditioiied types; and ( 2 ) the reasonable average strain to which t i m e better conditioned types should he subjected. In approaching this problem the cotriniittee gave enrriest consideration t o what constituted a reasonable shock in transit and, after placing this tentatively a t a collision shock speed of 8 miles per hour, equalized this by means of earcfiil tests t o the shocks transmitted by the shock testing niactiine and thus arrived a t the %-inch component now required in the regulations. The wisdom of this actio11 has been sliown by (1) the almost immediate effect on the industry in spurring the development of better conditioned and improved carboys; and ( 2 ) a reduction in damage losses to railroads by more than 60 per cent for the first year and a furthcr large reduction the second year-a result rather astoiiishirig when it. is considered that considerable numbers of suhstandard carboys were still in service. Further improvement was made through betterments in sealing practice. The old method of sealing a earlioy by means of a vitrified stopper, covered over with plastic clay or plaster, burlap-wrapped and string-tied, was a practice productive of accidents and damaxe loss. This was remcdied by developing and prescribing: (1)A porous earthenware stopper, hard-burned m d impervious
to the action of acid-spillage proof and yet sufficiently porous t o vent any pressure which might be otherwise built up in the bottle. (2) A gasket made of treated (paraffin and oil) asbestos wicking-proof sffainst the action of the acid. (3) Metallic seals easily applied and not readily destroyed through gas or acid contact. (4)A lip surfacing machine for repairing or surfacing away depressions in the Lips of carboys chipped during course of ser-ace. The development of this mach;ne made possible regula-
1057
tian! forbidding use of chipped lipped carboys for transportation SerYICe.
Tlie I. C. C. regulations furt,her provide for semiannual tests on each type of carboy used for transportation service, one of which is made by an inspector of the Bureau of Explosives. A11 users of acid in carboys should nbserve the regulation providing for the complete emptljing of carboys before their presentation to the carrier for return. More accidents occur through spillage of acid on workmen from supposedly empty earboys than from all other causes iii their handling. A safe practice is to fliisii the crnpty carboys with water and drain them thoronglily. Carboys loaded in cars for return should he loaded solidly nnd sliould he well braced t,o prevent shifting. ildcqiiate h r a h g is chcnper than broken carboys. Furthermore, enipty carboys should never be loaded on their sides with the necks hutting against the bottom of carboys in next row. Drums
This package would seem to he an ideal one for the safe transportation of sulfuric and mixed (nitrating) acids. Various conditions, however, must be taken into consideration: (1) The metal must be of sufficient gage t o withstand severe transportation and dropping strains, with a margin of safety to care for deterioration during scrvice. (2) The welded seams must be free from carbonized or oxidized spots, for unless these are 100 pcr cent perfect the wid will search out the defect. .
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I Carbag Testing Mechlne
(3) The inspection and testing service before filling should be efficient and carefully supervised. Inspected drums only should be filled. 14) Drum ~ l u rshould be seated on a msket made of ashestas . rope'wicking: (5)Repairs should not he made on a drum until it has been thoroughly washed out with 8 soda ash solution or some other neutralizint. anent. Even with this orecaution there is Dossihle danger fro& &impen gas: when making repairs an open 5ame should he used with the utmost caution, if a t all.
1058
INDUSTILIAL A N D fiNGINBBRING CIIBMISTRY
D r u m cannot be used with safety for transporting the weaker strengths of sulfuric acid. The Interstate Commerce Commission regulations place the minimum at 65’ B6, 60” F. This minimum was arrived at after careful tests showed that erosion of the steel took place very slowly in t,he presence of the higher concentrated strengths of acid, whereas below the minimum set the erosion was increasingly rapid with reductions in acidity. All users of drums should scrupulously observe the rule of storing filled drums in a cool place, not exposed to the direct rays of the sun. Acid is volatile; liquids of any w r t expand under increase of temperature. Full drums in stock should he stored with the plugs up. Internal pressure can be avoided by loosening the plugs occasionally.
Carboy LIP Grinding Machine
Great care should be exercised in rernoviog the drum plug. A long-handled wrench should be used and the operator’s face should be turned away froin the plug, for should the drum be under “built up” pressure, acid is liable t,o spurt from the opening. The safe way is to give the plug a full turn and if escaping pressure is apparent, allow the pressure to escape before loosening the plug further or removing it. When discharging contents no pressure should be applied. The gravity discharge method only should be employed. Interstate Commerce Commksion Specification 5-A prescribes the gage of metal, detail of construction, testing, etc., under which conditions this package can be legally used. Acid Tank Cars (Sulfuric and Mixed Acid)
This equipment is fairly well standardiled. The eonstruction of the underframe must conform to American Railway Association regulations. The desim of dome, tvue of fittines. and other equipment detail vary to suit’ tbe individ&i experience and development. Certain procedure must be followed however, one requirement being a s d e t y vent, attached to the dome fittings, equipped with a frangible disk, calculated to rupture at a pressure of 30 pounds. This takes care of “built-up” or internal pressure which may occur through rises in temperature, wlricli expsiids the acid. An air cushion to provide for this expansion consists of a dome capacity equal to 2 per cent of the total capacity of the tank. No tank car should at any time be filled with acid level higher than the base of the dome. Ordinary precautions should not he dispensed with when connecting up for the discharge of the tank. A small pressure (under the 30-pound rupture point of disk) may be present and this should he relieved bv ouenine the air valve, the workman should protect his Face- andeyes
Vol. 17. No. 10
against possible vapor when removing tlie cap or opening the valve on the acid discharge pipe fitting. Care should be taken to see that the fittings to the discharge line are in good order and the coupling pulled up tightly; otherwise spurting of acid might occur when pressure is applied to discharge the tank. Substitution of rubber hose connections for steel fib tings in connecting up the tank with the acid discliarge line is bad practice and should not he permitted. A recent survey of tank-unloading practice by large consumers of acid disclosed serious violations of the instructions stenciled on the domes of the tanks. A maximum of 30 pounds air pressure is permitted, which is sufficient to discharge the acid to a height of approximately 28 feet. Tank cars were found connected up with air mains under 100 pounds pressure with no reducing valve control. Such practice is dangerous and should not be permitted. Where conditions necessitate transferring acid long distances or to ~ elevations requiring in excess of 30 pounds air ~ T C S S U T to discharge, pumping should be resorted to. The t.anks on tank cars are containers and transportation units, not blowcases, and they should never be used as such. There is danger that the hydrostatic strain test as stenciled 011 the equipment be taken as indicative of the pressure that cull be exerted in discharge operations. No ouc conversant with the testing and maintenance of boilcrs or other pressure eqiiipinent would consider operating such a unit under workiug pressures equal to those exerted under special testa. A safety factor of 2 to 1 is not excessive; therefore, the stcociling on the domes of tank cars limiting pressure for disclmrge to 30 pounds. That this practice has been wise has been demonstrated by the infrequency of acid leakage in transit and the rarity of cmes where the tank or dome has “let go.” In the few cases which have come under observation, the darnage was caused by the excessive pressures exerted. Dry air should be used in blowing because of the effect of moisture on the interior of the dome and shell. It is good practice t o blow out the air line before connecting up. Naked lights should never be used around the dome of a tank car, whether loaded or empty. There may be hydrogen gas p r e s ent. All filled tank cars are protected in the course of t r a n s portation by the White Acid Label, as required by tlie Bureau of Explosives under the authority of the Interstate Commerce Commission. The presence of this label makes it the duty of all railroad employees to exercise unusual care in handling the car. It also places an obligation 011 receivers of this equipment to remove these labels as soon as the tauk car has been discharged. Orders from the trade calling for a definite tonnage less than tlie capacity of a tank car sornetinies give rise to a dangerous practice-that of partially filling the tank. This should never be done; the movement of the acid under end shocks in course of transit puts the tank under an unnecessary strain and may damage the tank or shift it froin its anchorage. The care used in washing a tank has a direct hearing 011 its life. The introduction of water develops heat, forms a dilute, sour solution, which acts readily on the sliell. This can he considerably reduced by introducing slaked lime or soda ash early in the washing. The regulations provide for the testing of tanks by either water or acid; in the lattcr case the dome is filled with acid, and when the test is coiiiplete, by siphoning out the acid in the dome, it is ready for the road. This reduces the washings necessary and adds to the life of the shell. Aceordine to the Bureau of Mines, the production of sodium compounds, not including common salt, from natural salines and brines in the United States in 1924 amounted to 76,420 short tons.
