M a r y a n P . M a t u s z a k , 709 Forbes S t., P ittsb u rgh , P a.
H
e r e t o f o r e , c o n -s t a n t - p r e -s -s u r e ga-s- analysis a p p a ra tu s has been of tw o general types, b e st d e s i g n a t e d b y th e n am es of H em pel a n d O rsat.T h e Ile m p e l ty p e is c h aracter
ized b y th e use of a n u m b er of in
div id u al a b so rp tio n p ip ets, each in its ow n su p p o rt o r fram e, w hich arc connected a n d discon
n ecte d in tu r n to th e gas b u ret.
B esides being a c c u r a t e , th is system is flexible a n d ad ap ta b le.
D ifferent k in d s of gas m ix tu res c an be analyzed w ith o u t change of eq u ip m en t. N ew o r special
a b so rb en ts can be em ployed in a d d itio n a l p ip ets w ith o u t an y lim ita tio n as to n u m b e r. N ew an d b e tte r devices can be ad d ed to th e e q u ip m en t w ith o u t d iscard in g th e old. T h e a p p a ra tu s, how ever, is b u lk y a n d n o t re a d ily m a d e p o rta b le , in sp ite of changes in th e d irection of m ore co m p act p ip ets, such as de
scribed b y A ugustin (1). M oreover, i t is in co n v en ien t an d tim e-consum ing because of th e m a n y connections a n d dis
connections.
T h e fam iliar O rsa t ty p e is ch aracterized b y h av in g a fixed fram e, a fixed n u m b e r of p ip ets, a n d a fixed m anifold. T h is com bination overcom es th e d isa d v a n ta g e s of th e H em p el ty p e, b u t on ly a t th e sacrifice of alm o st all flexibility a n d a d a p ta b ility a n d freq u en tly of considerable accuracy.
T h e u n itized gas-analysis eq u ip m e n t described in th is p ap er com bines th e a d v a n ta g e s of b o th th e H em pel a n d O rsat ty p e s an d elim inates th e ir d isad v an tag es. I t is th e re s u lt of a n e ffo rt to elim in ate th e o b jectio n ab le fe a tu re s of tr a d i
tio n al gas-analysis a p p a ra tu s a n d to develop a m ore sa tis
facto ry a n a ly tic a l tool. N o less th a n a fu n d a m e n ta l red e
signing of a p p a ra tu s h a s b een fo u n d necessary to m e e t th e needs of m o d ern gas a n a ly tic a l w ork. T h e changes in tro duced h ave increased sim plicity, accu racy , convenience, or usefulness.
Re c e n t Li t e r a t u r e
A side from d e scrip tio n s of m in o r changes or im provem ents, th e re c e n t lite ra tu re co n ta in s b u t few articles t h a t d eal w ith th e fu n d a m e n ta l design of gas-analysis e q u ip m en t, p erh ap s th e b e st know n of these, especially in A m erica, being Shep
h e rd 's (IS ).
T h e a p p a ra tu s described b y S h ep h erd is a n im p ro v em en t ov er th e u su al O rsa t a p p a ra tu s in such d etails as a m e ta l fram ew ork th a t p e rm its g re a te r accessibility to th e various p a rts, a b u re t illu m in ato r, a m ore efficient bu b b lin g p ip e t for th e rem oval of oxygen, a n d a special stopcock for controlling th e flow of m ercu ry . I t is, how ever, su b je c t to a n u m b er of criticism s t h a t h a v e u n d o u b te d ly m ilita te d ag a in st its ad o p tio n . I t is som ew hat com plicated in co n stru c tio n a n d operation. I t s ran g e is lim ited b y th e absence of a copper oxide tu b e. T h e large n u m b e r of stopcocks— tw o fo r every p ip et— necessitates m u ch ex tra handling, increases th e cost of th e a p p a ra tu s, a n d m u ltip lies th e d a n g e r of leakage.
F u rth erm o re, i t increases th e a m o u n t of d e a d cap illary space, w hich m u s t be corrected fo r b y tim e-consum ing “ sim ple
1 P a te n ts a p p lie d fo r.
a rith m e tic ” o r a d d itio n a l o p era
tio n s. T h e m anifold is b u ilt up of T -b o re sto p co ck s a f te r th e m a n n e r suggested b y P feifer (12), w ho devised th is a rra n g e m e n t fo r th e p u rp o se of m a k in g th e m an ifo ld flushable. I t is n o t, how ever, flushable in th e m o d ern sense, as are m anifolds b u ilt u p of 120° th ree-w ay s to p cocks (2, 11) o r of th re e -w a y stopcocks h a v in g special L- o r V -bores (5 ,7 ). T h e s h o r t len g th of th e b u re t, if n o t accom panied b y a n y loss of a c c u r a c y , has m ad e i t m o re confusing to read , a s i t is g ra d u a te d in fifths of a m illiliter in s te a d of in te n th s . T h e w a te r ja c k e t is un n eces
sarily expensive because of its larg e d ia m e te r an d th e a d d i
tio n al glass-blow ing involved. T h e a p p a ra tu s is h ea v y a n d n o t re a d ily m a d e p o rtab le, being designed fo r la b o ra to ry w ork only.
A n o th e r a p p a ra tu s developed in th is c o u n try is t h a t d e signed for use in th e la b o ra to rie s of th e su b sid ia ry com panies of th e U . S. S teel C o rp o ra tio n (5). T o e lim in ate th e need for m o re th a n one a p p a ra tu s fo r d ifferen t k in d s of gas m ix
tu res, all th e devices in g eneral use o n d ifferen t O rs a t a p p a ra tu s a re com bined in to o n e assem bly. T h is assem bly h as six a b so rp tio n p ip ets, a slow -com bustion p ip e t, a n explosion p ip et, a n d a copper oxide tu b e , to g e th e r w ith th e necessary electrical eq u ip m e n t. T h is a rra n g e m e n t n ecessita tes th e p u rch ase of m u ch e q u ip m e n t t h a t is b u t seldom if e v er used, a n d aside from th e in tro d u c tio n of a new flushable m anifold
(7), p re se n ts no im p ro v e m e n t of fu n d a m e n ta l design.
A g re a te r divergence from th e tra d itio n a l O rsa t a p p a ra tu s is t h a t developed a b ro a d b y B a h r (2). T h e a p p a ra tu s is m a d e in tw o p a rts, o n e fo r th e a b so rp tio n o p eratio n s a n d one fo r th e com b u stio n analysis. E a c h is p ro v id ed w ith its ow n b u re t, so t h a t a second sam ple can b e un d erg o in g ab so rp tio n w hile th e first is u n dergoing com bustion. C o m b u stio n is effected w ith tw o cop p er oxide tu b e s , one b ein g h e a te d to 300° C . fo r o x id atio n of h y d ro g en a n d c arb o n m onoxide an d th e o th e r to 900° C. fo r o x id atio n of m e th a n e a n d e th a n e . T h e accessory a p p a ra tu s fo r flushing a n d h e a tin g th e tw o cop p er oxide tu b e s m ak es th is a p p a ra tu s to o b u lk y a n d th e o p eratio n s to o involved.
A m o re co m p ac t a rra n g e m e n t described b y V ossieck an d S chm itz (15) co n ta in s tw o b u re ts b u t on ly one c o p p er oxide tu b e , w hich is used fo r h y d ro g en a n d c arb o n m onoxide.
M e th a n e , m ixed w ith a ir o r oxygen, is oxidized o v e r a h o t p la tin u m w ire in a q u a rtz cap illary . I n th e ab sence of eth an e , th e red u ced copper oxide m a y b e sim u ltan eo u sly reoxidized.
A n o th er a p p a ra tu s co n ta in in g tw o b u re ts is described b y B u rk h a rd t, F ischer, a n d F ra n k (3). O ne b u r e t is of sm aller volum e th a n th e o th e r an d is used for th e com b u stio n w ork.
A n in te re stin g a rtic le b y N e u m a n n a n d S trä h u b e r (10), w hich d eals w ith th e design of gas-analysis a p p a ra tu s of th e O rsa t ty p e , p re se n ts co m p lete d e ta ils of th e a p p a ra tu s used b y th e W arm estelle a t D üsseldorf, in clu d in g scale d raw ings of th e d ifferen t p a rts . I t also gives arw u n u su a lly th o ro u g h co n sid eratio n of c ap illary error, b u t p re se n ts no im p o rta n t changes in fu n d a m e n ta l design.
N o successful effort a p p a re n tly h a s b een m a d e hereto fo re C onslant-pressure gas-analysis equipm ent has
been devised which utilizes the advantages an d discards the disadvantages o f the H em pel and Orsat system s, com bining the fle x ib ility a n d a dapt
ability of the one w ith the convenience, com pact
ness, an d ra p id ity of the other. The apparatu s consists of complete self-contained u n its that fasten together to fo rm a n y desired assem blies of
the Orsat type.
A number of improvements have been devised that have sim plified gas-analysis equipm ent and its m an ipu lation , an d increased its accuracy, convenience, an d usefulness.
72
Jan u ary 15, 1934 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y 73 to com bine th e flexibility an d a d a p ta b ility of th e H em pel
sy stem w ith th e com pactness, convenience, a n d ra p id ity of th e O rsa t sy stem . A s t a r t in th e p ro p er directio n , how ever, h as been m a d e b y d iscard in g th e fragile, inflexible, one-piece m anifold. F o r exam ple, B a h r (2), Vossieck a n d Schm itz {15), a n d O tt (11) h av e a d o p te d p ip e ts te rm in a tin g a t th e to p in th ree-w ay stopcocks of th e 120° ty p e an d h ave shifted th e ru b b e r connections from th e v e rtic a l bran ch es to th e ma i n line of th e m anifold.
Ad v a n t a g e s o f Un i t i z e d Ap p a r a t u s
B o th precision a n d tech n ical assem blies of th e unitized g as-an aly sis eq u ip m e n t are show n in th e illu stra tio n s. P re cision assem blies are cap ab le of th e m o s t e x a c t w ork th a t can be perfo rm ed w ith assem blies of th e O rsa t ty p e . T ech nical assem blies arc lim ited to a low er d egree of a c c u ra c y b y th e sh o rte r len g th of th e b u r e t a n d th e absence of a com pen
sa to r. A tech n ical assem b ly is m a d e p o rta b le b y sim ply being p ro v id ed w ith a ca rry in g case.
T h e chief d e p a rtu re from th e tr a d itio n a l O rsa t design is th e division in to in d iv id u a l self-contained u n its, each including its sh a re of th e fram ew o rk a n d m anifold. T h is change p e rm its th e b u ild in g of a n y assem bly, from th e sim p lest one- p ip e t ty p e to th e m ore com plex sev eral-p ip et ty p es, from sta n d a rd u n its. T h e sam e re a c tio n u n its are used in b o th precision (la b o ra to ry ) a n d tech n ical (p o rtab le ) assem blies, a n d a n assem b ly can b e ex p an d ed a t a n y tim e b y th e a d d itio n of m ore u n its. F o r exam ple, a fra ctio n al-co m b u stio n o r cop
p er oxide u n it can be a d d e d w ith o u t expensive a lte ra tio n s in m anifold o r fram ew ork. D evices em b o d y in g fu tu re im p ro v em en ts in a p p a ra tu s o r tech n ic can be a d d e d w hen de
v eloped w ith o u t d iscard in g a n expensive piece of eq u ip m en t.
R eferrin g to th e a p p a ra tu s designed fo r th e U . S. S teel C o rp o ra tio n (5), i t is e v id e n t t h a t a co rresponding assem bly can be b u ilt from th e new u n its. C e rta in a d v a n ta g e s are im m e d ia te ly a p p a re n t. T h e u n itiz e d assem bly is n o t lim ited b y th e fram ew o rk o r m anifold a n d can th erefo re be exp an d ed or c o n tra c te d a t will to m eet special req u irem en ts. T h e o p era
to r can a rra n g e th e u n its in w h atev er o rd er he considers best—fo r exam ple, th e b u re t can be placed a t eith e r th e rig h t o r th e le ft e n d of th e assem bly, o r tw'o b u re ts can be incor
p o ra te d . T h e se can be of d ifferen t designs to d eal m ore ad e
q u a te ly w ith d ifferen t k in d s of gas m ix tu res o r to co n d u ct th e co m b u stio n o p eratio n s m ore a c c u ra te ly ; or, th e y can be used to p e rm it ta k in g in a new sam p le a n d su b jectin g i t to th e ab so rp tio n p ro ced u re w hile th e old is undergoing th e com bus
tion an aly sis. O th e r in c id e n ta l a d v an ta g es, such as a n all- m etal fram ew ork, g re a te r accessib ility of p a rts, g re a te r ease of rem o v al a n d cleaning of glassw are, elim in atio n of th e u n necessarily larg e size of th e in s tru m e n t panel a n d safety-glass shield, g re a te r flexibility, sm aller fra g ility of glass p a rts, elim i
n atio n of d e a d cap illary space, etc., will be a p p a re n t fr om th e d escrip tio n of th e e q u ip m en t.
Fr a m e w o r k
T h e fram ew o rk is e n tire ly of m etal, em ploying a lu m in u m al
loys w h erev er possible. S tu rd in ess, d u ra b ility , a n d full ac
cessibility to all p a rts h av e b een achieved. A ll p a rts are sy m m etrically designed to p e rm it s ta n d a rd iz a tio n a n d in ter- ch an g eab ility .
T h e fram ew o rk a llo tte d to each re a c tio n u n it consists of tw o p a rts . O ne is a b a c k piece, b o lted to id e n tic a l pieces in o th e r u n its o r to a clam p on a fram e s u p p o rt, from w hich ex te n d s a v e rtic a l ro d c a rry in g a p h osphor-bronze clip for securing th e to p of th e re a c tio n vessel. T h e o th e r is a v e rti
cally a d ju s ta b le shelf piece, cu p -sh ap ed a n d lined w ith felt for p ro te c tio n of th e a b s o rp tio n p ip ets.
T h e tw o v e rtic a l fram e su p p o rts fo r tech n ical assem blies
consist sim p ly of half-inch (12.7-nun.) alu m in u m ro d s a b o u t 50 cm . long, im b ed d ed in c ast-alu m in u m feet. T h e y can be screw ed o r b o lted to a n y a p p ro p ria te base, such a s th e b o tto m of a carry in g case, a n d are p ro v id ed a t th e to p w ith rem ovable b o ttle -re sts w hich also serve as guides w hen slipping a case dow n o v er th e assem bly.
F i g u r e 1. U n i t i z e d P r e c i s i o n T i m e - S a v e r G a s A n a l y z e r
E a c h su p p o rt for precision assem blies consists of th re e p a ra l
lel stain less-steel rods, a b o u t a m e te r long, in a sta g g e re d o r V -fo rm atio n w ith tw o ro d s in th e lin e of th e re a c tio n tr a in a n d th e th ird o r m id d le ro d se t b ack a b o u t 75 m m . T h e y a re h eld to g e th e r b y a lig h t rem o v ab le a lu m in u m to p piece, a n d b y b ra ss fe e t w hich a re b o lted o r screw ed to a ta b le or o th e r a p p ro p ria te base. T h e th re e ro d s a t each e n d of th e assem bly s u p p o r t th e tr a in of re a c tio n u n its, th e m easu rin g u n it, th e sam p lin g b u lb , a n d th e v a rio u s lev elin g b ulbs.
Ma n i f o l d
T h e m an ifo ld is b u ilt u p of sto p co ck s w hich are in teg ral w ith th e v a rio u s p ip e ts o r o th e r re a c tio n vessels, joined to g e th e r b y h o riz o n ta l r u b b e r connections. T h is p e rm its a m ax im u m of flexibility a n d a d a p ta b ility w ith a m in im u m of frag ility .
T h e n u m b e r of ru b b e r co n n ectio n s h a s b een d ecreased.
F o r exam ple, in th e w ell-know n B u re a u of M in es assem b ly (4, 6) th e re are te n ru b b e r con n ectio n s, one of w hich h a s been e lim in a te d in la te r m o d els; in th e c o rresp o n d in g u n itized assem b ly th e n u m b e r h a s b een red u ced to seven. I n general, th e n u m b e r of ru b b e r co n n ectio n s w ith w inch th e sam p le can com e in to c o n ta c t d u rin g th e a n a ly sis p ro p e r h a s been red u ced
n A N A L Y T I C A L E D I T I O N Vol. 6, N o. 1 b y one in all m odels n o t h av in g a cop p er oxide tu b e , a n d by
tw o in all t h a t do include such a device.
D ead cap illary space in th e v e rtic a l b ran ch es is p ractically n o n ex isten t. T h e rea g e n ts can be d raw n u p alm o st to th e stopcock. U nlike th e 17. S. S teel C o rp o ratio n a p p a ra tu s referred to above, th is can be done w ith o u t th e ab so rb e n ts
Fi g u r e 2 . Un i t i z e d Pr e c i s i o n Mi n e- Ai h An a l y z e r
com ing in to c o n ta c t w ith ru b b e r connections. Also, th e ru b b e r connections a re n o t c o n tin u o u sly su b je c te d to th e actio n of a b so rb e n ts o r th e ir v a p o rs w hen th e a p p a ra tu s is idle.
F o r elim in atio n of cap illary e rro r th e m anifold sh ould be filled w ith n itro g e n a t th e beg in n in g of a n analysis. A m ore aw kw ard an d tim e-consum ing pro ced u re is to fill th e hori
z o n tal cap illary writh a c id u la te d w a te r o r m e rc u ry from th e slow com bustion p ip e t o r from a n au x iliary p ip e t. Since such devices as m an o m eters a n d cop p er oxide tu b e s can be flushed only w ith in e r t gas, th e use of liq u id s to elim inate cap illary e rro r is n o t to be recom m ended. O n th e o th e r h an d , i t is desirable to be able to u se a c id u la te d w a te r fo r w ashing o u t a n y a b so rb e n t d ra w n in to o r b e y o n d th e bo re of a sto p cock, w ith o u t d ism an tlin g th e assem bly a n d w ith o u t loss of th e sam ple.
T h e new m anifold is m ore p erfectly flushable a n d m ore easily cleaned th a n a n y o th e r know n to th e a u th o r. T h is h a s been achieved b y its stra ig h t-lin e design a n d th e use of s tra ig h t-b o re th ree-w ay stopcocks.
T h e principle of o p eratio n of th e stra ig h t-b o re th ree-w ay stopcock is th e sam e as t h a t of th e 120° stopcock, b u t th e co n stru ctio n is different. Tw o of th e arm s a re in th e sam e s tra ig h t line, w ith th e th ird a t rig h t angles. T h e plu g h a s a single, s tra ig h t, eccentric bore. T h is co n stru ctio n m ak es it possible to p ass a len g th of co tto n -co v ered w ire com pletely th ro u g h th e m anifold from one en d to th e o th e r w ith o u t re
m oving a n y plugs. O th e r flushable m anifolds h a v e th ree- w ay stopcocks w ith bores of a n L - o r Y -shape (5, 7).
All stopcocks u sed in th e u n itized m anifold are id en tical
in co n stru ctio n a n d o p e ra tio n . T h e fo u r-w ay stopcock on th e fra c tio n a l co m b u stio n u n it is b u t a n a d a p ta tio n of th e stra ig h t-b o re th re e -w a y sto p co ck , a n d is m a n ip u la te d ex actly like th e o th ers. E v e ry sto p co ck h a s th e sam e re la tiv e posi
tio n , w ith tw o arm s h o rizo n tal, th e th ird dow n w ard , a n d th e h an d le to th e fro n t. T h is sim p lificatio n a id s th e o p e ra to r to m a n ip u la te th e sto p co ck s w ith o u t ex am in in g th e m to d e te r
m ine th e p o sitio n of th e plug. T h e u su al precision O rsa t a p p a ra tu s h as th re e or m ore d ifferen t k in d s of stopcocks— th e S h ep h erd a p p a ra tu s h a s five, n o t in clu d in g th e c o n tro l sto p cock a t th e low er en d of th e b u re t— a n d th e se are som etim es placed w ith h a n d le s to th e side in s te a d of to th e fro n t.
Bu r e t s
All b u re ts are p ro v id ed w ith one sto p co ck a t th e to p . T h e ir sy m m etrical c o n stru c tio n p e rm its a n u n u su a l flexibility of a d a p ta tio n .
P r e c i s i o n B u r e t s . R e d u c in g th e n u m b e r of stopcocks on th e precision b u r e t to one p e rm its i t to be ra ise d re la tiv e to th e re a c tio n tr a in , a n d to be re a d w ith g re a te r ease a n d com fort. I t also p e rm its in creasin g th e le n g th of th e g ra d u a te d section, th u s m a k in g th e sp acin g of th e g ra d u a tio n m a rk s som ew hat g re a te r a n d c o n trib u tin g to th e a c c u ra c y a n d ease of read in g .
T h e change h a s also d ecreased th e fra g ility of th e b u re t, an d low ered m a in te n a n c e cost. F ew er ru b b e r connections re
su lt in a g ain in flexibility a n d in freedom fro m stra in s . Precision b u re ts ha v e a n over-all le n g th of 87 cm ., a g ra d u a te d section of a b o u t 70 cm ., a n d a c a p a c ity of 100 m l.
T h e g ra d u a tio n s a re black, m ore p e rm a n e n t th a n th e u sual w h ite ones, a n d s ta n d in g o u t in sh a rp e r c o n tr a s t a g a in s t th e back g ro u n d afforded b y th e w7a te r ja c k e t. T h e g ra d u a tio n s in clu d e th e bore of th e stopcock.
T h e la te s t sty le of g ra d u a tio n s is u sed . W hole m illiliter m a rk s e x te n d com pletely a ro u n d th e b u re t, for elim ination of parallax, a n d ev en m illiliter m a rk s a re n u m b ered . T h e o th e r m a rk s ex ten d a ro u n d a p o rtio n of th e b u re t b u t n o t halfw ay. T h is sty le of g ra d u a tio n s is as a c c u ra te as th e so- called “ U . S. B u reau of S ta n d a rd s sty le of en g rav in g ” an d is m o re ra p id a n d easier to read , because im m ersion of th e b u re t in w a te r causes m agnification o r even th e a p p earan ce of a d d itio n a l im ages or reflections of each g ra d u a tio n m a rk . I f half-circles are p re s e n t th e re su ltin g m aze of m a rk s a n d th e ir im ages is d is tra c tin g a n d tireso m e to th e eye, p a rtic u la rly as th e m a rk s are u su ally placed m u ch closer to g e th e r th a n re c om m ended b y th e B u re a u of S ta n d a rd s (14)- How'ever excellent half-circles m a y be on o th e r pieces of la b o ra to ry glassw are, th e y c o n stitu te a decided h a n d ica p on gas b u re ts.
Precision b u re ts are of tw o p rin cip al m odels. T h e u n i
versal m odel is of u n ifo rm bore, g ra d u a te d in 0.1 m l., a n d is
versal m odel is of u n ifo rm bore, g ra d u a te d in 0.1 m l., a n d is