claim as my invention: 1. Apparatus for determining the pore volume distribution of a porotis solid which comprises in combination a fluid-tight chamber defined by a substantially 55 rigid longitudinal cas:ng and a pair of end closure members, o@ic of said end closure members comprisin- a remova'ole sealin.- member, and the other of said end closure members comprisipg a bellows which is expandable inwardly of the chamber, a shaft connected 60 to the free end of the beilows and extending through the bellows to the exterior of said chamber, valved conduit means communicating wi@th the interior of said chamber, means for introducing a fluid under pressure to the interior of said bellows, means for varying the 65 pressure of said fluid, means coupled to said shaft outside the chainber for measuring shaft displacement, and means for measuring the pressure within the chamber. 2. The apparatus of claim I further characterized in 70 that a perforate sample container is disposed within said chamber and is connected to said removable sealing niember. 3. The apparatus of claim 1 further characterized in that a passageway extends through said removable seal- 75 ing mer.,xber, said valved conduit means connecting with said passa-,eway. 4. Apparatus for determining the pore volume distribution of a porous solid which comprises in combination a fluid-ti.-ht ebamber defined by a substantially ri-jd longitudinal casin.- and a pair of end closure members, one of said end closure members comprising a removable s@-aling member and the other of said end closure members co@nprising an elastic bellows disposed within said chamber and free to expand inwardly thereof, a bellows seating member maintaining the fixed end of said bellows in fluid-tight contact with said casing, a passageway extending through said seating member con-hiiunicating at one end thereof with the interior of the bellows and being provided at the other end with a shaft seal, a shaft of smaller diameter than said passageway con@lected to the free end of said bellows and extending through said passageway and said shaft seal to the exterior of said chamber, means coupled to said shaft outside the chamber for measuring the displacement of the shaft, a fluid supply conduit communicating with said passageway, and v,@Iv,-,d conduit means communicating with the interior of said chamber. 5. Apparatus for determining the pore volume distribution of a porous solid: which comprises in combination a fluid-tight chamber defined by a substantially rigid lor,@itudinal cas,@'n,- and a pair of end closure members, one 6f said end closure members comprising a removable r@.gid sealing member and the other of said end cl@osure members coniprising an elastic bellows disposed within said chamber and free to expand inwardly thereof, a bellows seating member maintaining the fixed end of said bellows in fiuid-tight contact with said casing, a perforate sainple container disposed within said chamber and connected to said removable sealing member, a passa.-eway extending through said belloivs seating member communicating at one end thereo' w:th the interior of said bellows and being pronided at the other end with a shaft seal, a shaft of smaller diameter than said passa,-Cway.connected to the free end of said bellows and extending through said passageway and said shaft seal to the exterior of said eliamber, means coupled to said shaft outside the chamber for measiuing the displacement of the shaft, a fluid supply conduit communicating vp'th said passageway, and valved conduit means communicating with the interior of said chamber. 6. ADparatus for determining the pore volume distribution of a porous solid which comprises i-n combination a fluid-tight chamber defined by a substantially rigid longitudinal casing atid a pair of end closure members, one of said end closure members comprising a removable rigid sealing member and the other of said end closure members comprising in elastic bellows disposed within said chamber and free to expand inwardly thereof, a bellows seating rnerber maintaining the fixed end of said bellows in fluid-tight contact with said casing, a perfora@le sample container disposed within said chamber and con-@iected to said removable sealing member, a passageway extending tbrough said bellows seating member communicating at one end thereof with the interior of said bellows and being provided at the other end with a shaft seal, a shaft ol' smaller diameter than said passageway connected to the free end of said bellows and extending through said passageway and said shaft seal to the exterior of said chamber, means coupled to said shaft outside the chamber for measuring the displacement of the shaft, a flu-id supply conduit commun-leating with said passageway, valved conduit means communicating with the interior of said chamber, and pressure sensin.- ricans responsive to chamber pressure. 7. Apparatus for determining the pore volume distributioii of a porous solid which comprises in combination a fluid-tight chamber, ap-.rforate sample container for said porous solid in one end portion of the chamber, an

311583020 7 elas'lic bellows sealin.- the other end of the chamber ana References Cited in the file of this patent expansible within the chamber toward the sample conUNITED STATES PATENTS tainer, a shaft connected to the fr--e end of said bellows 2,296,852 Homer ---------------- S,-,pt. 29, 1942 and extendin.- through the bellows to the exterior of said 2,604,779 Purcell ---------------- July 29, 1952 chamber, means for filling the chamber with a liquid, '5 2,662,393 Rzasa ----------------- Dec. 15, 1953 means for introducing a fluid u-@ider pressure to the interior 2,692,497 Van Nordstrand -------- Oct. 26, 1954 of said bellows, means for varyirig the pressure o,' said 2,957,334 Essmann -------------- Oct. 25, 1960 fluid, and means coupled to said shaft outside the chamFOREIGN PATENTS ber for meastiring the displac-,ment of the shaft. 10 973,471 Germany --------------- Mar. 3, 1960

United States Patent Office 3@1582020 r "3 5 E,/i W- T E, T" George R. Donaldson, Eirr-@'nglon, Ill., assig--@,3r to U--iversl,l Ci't Prod4-ts Com-on-@l-y, D-e-9 -'K'LqLres, Ill., a rc@rperation o' Dela-,vare 5 Fi'@ed JLEze 14, 1961, Ser. No@ 117,033 7 C!a@- ms. (Cl. 73-38) This invention relates to apparatus for the determination of pore -,,olume distribution of porous solids - titiliz- 10 ing the hydraulic penetration technique. More part;cL,- larly, this invention is direrted to an ir@iproved me@,cruy porosim eter designed for operation at pressures rangi.'I,- fro@n substantially zero p.s.i.a. up to 100,000 P.S.i.g. The determinilion of pore volurr@e jand pore volume 15 spectra by liquid int@rusion is :a well known ar-alytical method and need be only briefiy described here. In 'th;s techiiiqu e a sample of porous soh-'d is immersed i-@i a liquid which is selected so as to be substantially "-@ionwetting" with resrect to the solid, that is, the angi(,- 01 20 contact is large and ihere is ia repulsion o'll the iiiqiiid from the surface of the solid. In ore@p-r for liquid to enter a pore of a given diameter, a ce.-tain r@linimLIDI pressi,re must be applied to the system; this pressite is a function of pore diameter, stirface tensiola of the l,@,luid, 25 and ano.,Ie 6f contact and can be calculated accord;@D,a to known mathematical formulas. The minimum - d:.ameter of a pore which can be filled with liquid is appr6xiinately inversely proportional to the logarithm of -the arplied pressure ,, iall other vari-,tbles being h-.ld constant; there- 30 fore, the higher the pressure the smaller the d;ap-.eter of pore which is filled. As pressure is inereireiitally i,@icreased, the corresponding decrease in voliime of the solidliquid system rel)resents the total pore volti@ne of all pores having diameters between the penctratable m,.n;- 5 mums I correlative with the preceding lower pressure and the neyt higher pres3ure. By correlating chaige in volume ixiith cha-nge in pressure at several pres.-ure levels, the compl,-te distribution of pore volume as a functio-Ti of pore diameter may be obtained. Mercury is - almost 40 universal ly prefererd as the penetration liquid beca,,ise of its high negative capillarity with respect ito sol;ds, althou.-h other liqlids such as carbon tetraci2loride @aid ethylene dibromide have occasionally b-.Cn employed in this work. Liquids havin.- low surfac-. terision and small 45 contart anglb are unsatisfactory f<)r measurement of large dilamete r pores since these are readily fil'@ed at very low presstire s which are difficult to measure. I-I.-retofore the utility of mercury porosi-Tnetry h-,Ls been largely limited to determining the volume of macropores, that is, po.,es ro having diatneters ranging from about 100,000 A. down to abou@t 1200 A., at corresponding pressures ranging from sl;,-htl@ above atniosph-@r-ic to,about 1500 p.s.i.g. While pores of smaller diameter ca-@l be investigat.ed by resort to higher pressures, the h-,avy pressure equip- r,5 me-@it heretofore developed therefor has been - considered too expensi've, climbersome and inaccurate to permit use in routine analyses of micropore structures. For example, one common type of porosimeter employs a calibrated .-lass capillary tube disposed with@',n an armored 60 gauge glass, the mercury-pressuring fluid meniscus within the capillary being observed visually. The maxirnum pressure utilizablo here is severely I;Mited by the strength of the gauge -lass, and the glass panel itself'is quite expensive to replace should it become broken. 65 In conseqlience of the limitations of prior art apparatus, the investiration 6f micropore structure is usuahy done by the nitrogen adsorption method, which is satisfdctory for pore diameters within the range of from about 20 A. to about 600 A. 70 It is an object of ,he present invention to pro.vide a versatilo, exteiided range liqiid porosimeter capable of r@,'Iented Nov. 24, 1964 2 deteiniinin@ volumes of pores having diameters within the range o@f f-rom about 150,000 A. to about 56 A. In a broad embodiment, th-'@s invention relates to apparatus for determinin.- the pore volume spectrum of a porous solid which complises in com@ b-nation a fluidti,- it chamber de-lqned by a @@tibstantially rigid casing and a single resiliently deformable wall sectl:on, a shaft conn.-c,,Cd to said deformable wall sect,',on ektending exteriorly from said ciiamber, means for inserting a sample of porous solid into said chamber, means for filling said chamber with a liqiiid, and m.-a-.is for subjecting the exterior surface of sa,.d deformable vvall section to coiitact w:.th a @quid under adjustable pressure. A mbre si)e-.ific embodim-.nt of th@',s invention is directed 'to a porosimeter comprising in coinbination a fluid-tight chai-nber defined by a substant:@ally rigid longitudinal casing and a pair of end closure members, one of sa-ld e-tid closure members comprising a removable sealing member and the other of said end closure mentbers compri,,;iig an elastic bellows disposed within said charrber apd i'ree to expand invvardly thereof, a b6llows s-lating m,-mber mai@itaining the fixed end of said bel. lows in fluid-tight contact with sal:d casing, a passage,vay e,-,t-,nding through si,'@d seating niember communicating at o-@ic end thereof with the interior: of the bell6ivs and bc;,ig provided at the other end NVith a shaft seal, a shaft of smaller diame@ler than sa:d passa,-eway con nected tb the free end of said bellovis and extending through said passa,aeway and said shaft seal a fluid supply coiduit communicating with said pass'ageway, and valved condijit means corr@municating with the interior of said chamber. The structure aiid operation of this invention may best be despr@'bed in conjunction with the accomdanyina drawing which is rresented as illustrative of t@he bes't mode ol' practicing the invention but not with the intbntioti of unduly limit@ng its broad scone. Obvioiis modiflcal,iolis and substitution of equivafent elements in the specific adparatus ihtistrated will be readily apparent to those skifled in the art. WI ith ret'erer@ce r@ow to the drawin.al ther I e is shown a secl@ional elevation vivv of the present porosimeter. A tfiick-wa.Iled c@ilindrical casing I having a hollow interior 2 of limi'Led valu-m@ e is seal,-d at its uPT)er end by a conically tipped h-,ad 3 which in turn is- urged into fluid-tight contact with casing I by threaded r-oihpres@ion collar 7. An 0-ring 6 is R' ted ;nto conical sutfac6 5 of head 3 to provide additional sealing effect. A passage@vvay 4 for vacuumevactiatioi and mercury filling i@ drilled through head 3. A sample cont,,iiner 3, which may be a wire basket or otlier t-ype of Pei-forated 8hell member suitable for retainin,@. the poroiis so'id as a con'@ined mass in open co-tnrqu,nication with space 21 is removably attached to heact 3 by means of clips 9. Casing I is sealed@ a@t its lower end by an elastic, e@- ,@iafsible bellows 10 dispos.-d w;thin space 2 and having a diarhp-t6r sliihtly smaller than the internal diameter bf cdsihg 1:. The lower fl-,ed end 11 of bellows 10 is flared o@il*afdly to conform with tl-.e bevele(f wall of casiiig I At that poiiit, and the upi)er free end of bellows 10 is- fittbd@ to a c-,ip pl,ate 12. A threaded coilipression cbllar 19'b@ar@ upwardly aaainst conically tipped head 14 wbich iii turn urge&flared end 11 of bellows 10 ino fliiid-fight coijtact with casing 1. An 0-ring 17 in conical siitfaco 16 cif head 14 and an 0-ri-@ig 18 in the adjiceiit b-@veled'wall of cas:.ng I provide further sealing 6ffeet' Ubper aiid lower bleed ports 20 are cut throli,@h the wqll of casing I to protect agai@ist possible pr6@suro build-i-ip in and around upper head 3 and lower hbad 14. The lower elongated exte-Tision of head 14 terminales in a Tfitting 21, and a passageway 1-5 is dtilled thb, length of head 14, coinmun;cating at its upper end with t@,o

sealed interior of bellows 10. A shaft 13, havin-. a smiller diameter than pnssa.-eway 15, is conneeled at its upper end to bellows cap plate @-2, and shaft 13 e,-tends downwardly through the length of pas3ageway 15 to the exterior of T-fittin.- 21. A hydraulic se,,il form-.d by 0-ring 22 and compression nut 23 seals thc, exit of shift 13 from T-fitting 21 wh4j-. per-,nittin.- free longit,,id;nil movement of the shaft. A fluid supply passageway 24 formed in T-fittin.- 21 comn-ilinicates with passageway 1.5. Casina I is immers--d in a constant t,,mperat@are bath 29 contained in tank 23. Any suitable means for cortrolling bath teniperat,.jre may be employed (not sliown) such as an immersion h,-at.-r and a paddl-. st,.rrer; alternatively, in lieu of a corsla@it t-.mp-- rature b-,th, casing I may be wrappcd with -,n adiabat;c la.-.-ing and a dift'er ential temper,,itlire co-.itroller connected thereacross. A third means of maintai-@iin.@ the apparaLLs at a constant temperature is to enciose the entire appa.-a@us iii a hot box in which a stream of air at controlled temperature is circulated, the temperature control b--in.- provded by a thermostatically controlled elec',ric h@-atin.- elemenl, heat exchan.-,-r, or otlier rneans; such arran,-ement has 'Lhe advantage of surroi-inding the entir,- apparatus, iricludin.- collars 7 and 19, with a constant tenperature niedium, thereby minimizing heat fiow through collars 7 and 19. The lower end of shaft 13 is connected via linka.--. 25 ar.d pivot 26 to a dial micromeler 27. A pressure generator 30 is connected via line 31 and valve 33 to passa.-eway 24, and a pressure ga,,iz--, '-72 is T'd i,@ito Iiiie 31. Th-- presstire @enerator may be a hand-powered hydraulic pistor, as iilustrated, or a niotor-driv-@ii iii.-h pressure pumt), or a co-itrollt,.ble source of compressed ,-as. The hydraillic fiuid may be a hydrocarbon oil, an alcohol, or arly other stiitable liquid or .-as. The operation of the apparatus is as folloivs: head 3 and sample container 3 are renioved, a ivei,-,hed sample of porous solid is placed in container 0, apd these parts are then reasseinbled and ti.ahtened up. A li@ie 38 is connected to passageway 4 wliieli in turn connects, alternatively, through I;ne 34 and valve 35 to a reservoir of mercury (- @lot shown), ard tiiroii.-h line 36 and valve 37 to a vacuum pump (not shown). @,llith valve 35 closed and valve 37 opeii, the sample atid hollow interior of casin-a I are evacuated of air, w,,iter vapor, and other fluid contaiuinants which may have a,,cum,,ilated within space 2 or have become absorbed withi-,i th.- pores of the sample. Valve 37 is then closed and valve 35 op@--ried, admitting n-iercury into spac@-- 2; wh,,n space 2 is completely filled wilh mer-,ljry, valve 35 is closed. Th@- fi'@l-@d and sealed apparatus is th-,,i allowed to reach the coltrolled temperature before the twt is commenced. Hydraulic fl@aid proni pressure so,,irce 30 flows through passagenvays 24 and 15 in,o the interior of bellows 10, causing the bellows to expand inv@ardly ;nto space 2, subjecting the mercury in space 2 to the same p@-essure as that of the hydraulic fluid, and forcing merciiry into the pore,sof.thesolidsampl-@. Asthebellowsexpands,@haft 13 moves upwardly and ifs displacement is registered by dial micrometer 27. After the test is completed, the apparatus may be depressured and the mercury may then be removed to the level of the bottom of cone 3 by aspirating mercury from passageway 4 before the collar 7 is loosened and removed. This same Epparatus may be utilized for studies at subatmospheric pressures, i.e., at pressures as low as substantially zero p.s.i.a., by means of a simple variation i.n the mercury Mling tech-nique. The mercury reservoir tank is vented to the atmosphere and placed at a suitable lower elevation than the porosimeter itself, the bottom of the rnercury reservoir bein- connected to conduit 34 as before. After the sample@of porous solid loaded into space 2 and the chan-iber bas been evacuated to substantially zero p.s.i.a., valve 37 is closed and valve 35 is opened, and atmospheric pressure acting upoi the niercury level within the reservoir forces the mercury to flow 3,158,020 eb upwardlythro,,,-Illine3e;intosp,,ice2. V,/henspace2and passagew,,iy 4 are f-@lled i,,,i,h mcreury, the absolute pressure existin.@ at the top of passa.-eway 4 is less than atmcspheric by ttic amoutit equivalent to tlc height of mercury coluir@ii in the fillin.- le.-, e.g., the difference in elevlt@o-@l belweei the reservoir level and the top of passa-,eway 4; this ab.@olute presslre may be niade substa,@itially zero prov;ded th-, hei.-ht of ,be v@-rtical fillin.- le.- equals or exceeds ,he existing atmosplieric, pressure as meastired in 10 -eni,s of len-Lh of n-ierc,,iry. Under these conditions, the test run starling pressure actin- upon the sample of porotis solid is only greater than zero p.s.i.a. by the hei,-ht of mercury contained in passa.-,-v@,ay 4., which need be only a few centirieters in length. It will be appreci-,ited that the in15 stant inic@ition -s well suited for very low pressure studies as well as hi.-h presslre work, and accomplishes in a single un;tary appar,-,tus those functions which heretofore have required two separale porosimeterassemblies, otic for subat-inospheric pressure and the other for superatmos?o pher-'@C pressure. I-vfater:lals of constrtiction may be sleel, st-,tinless steel or aiiy otlier mcl,,l havin- the requ:site yield strength, aid tiose parts oi the equlpl)ment whi'ch contact mercury sho,.tld, of course, not amal-aniate therewith; any of the 300 series stainless stec',s are stiit,@ible as construction m,-,terials for t'ne cas;n.-, heads, and sample container for prt-ssures up to about 30,000 p.s.i.; for hi.-her pressures up to 100,000 F,.s.i., it is preferred to use a 400 series stainless steel wliich is liprden@able and lias a higher yield 3o strength. Si.@ice the bello@N,s is st,,bject to very little differential prcsstir(, (a rq,,ixinium of 15 p.s.i. during evacuation) @.t P.-i--.iy b-. fabricaled of sziicably thin metal, i.e., ,04 or 316 st,,iinless steel, witli foremost regard in t]@e desi.-n tliereol. beiiig given to meeting deflection 55 specifications. The interior 2 of casin.- I is preferably for-rncd as sr@iall as praelictble to permit minimum inventory of mercury the..--,in. This is becalise the compressibility of niercury must be tal-,en into account at th.- hi.-her pressures, and eo while the decrease in volurne cbar.@-.able to cor@ipression of the mercury ca-@i be calibra'@ed out, the less volunie there is to contend v,,ith, the less chance for experimental error in any event. The diameter of bellows 10 is tlierefore made just sligl-tly smaller than the diameter of space 2, and the b.-Ilows Nvhen 'ully loigitudinally expanded approaches closely, but do-.s not quite contact, sample container S. V&ere the @-neasured pore volumes are small and o@-hy limited travel of shaft 13 is required, a deflectable diaphragm may be substitu'Lod for the bellows 50 member. Because shaft 13 is of small dia,-neter, it is easy to s--al ag@ainst hi.-h fiu@'d i)ressures. If d,@sired, a weighted wire may be used inslead of a ri.-id shaft for this pur pose, and such var-'@at;on is encompassed within the defini55 tio@l of the term "shafc' as herein employed in the specificat-on and i?i the appended clair@-is. However, a small rate of leakage around shaft seal 22 may be tolerated Nvithout difficulty since pressure source 30 will be able to provide additio-ial pressuring fluid as required. 60 Althou,@h passageway 4 is shown as extending through removable head 3, it will be appreciated that this passageway may instead be drilled throu-.h the longitudinal wall of the casing itself. The apparatus is preferablyvertically oriented, as illustrated, in order to aid in filling v,,ith mercury; honvever, it is not essential that it be oper65 ated vertically, but it may be operated in a horizont,,tl position, or obliquely to the vertical, or completely inverted, as desired. The pressure gauge and dial micrometer represent the 70 simplest means of measuring chamber pressure ap-d shaft displacement, respectively, and these instruments will suffice for nost routine analytical work. A standard microme'@er can respond, reproducibly, to differential displacements of the order of 0.0005 inch, and the present 75 porosi meter may readily be sized to provide a total shaft

31158,020 5 displaccrncr.t of 1-11/2 inches over an applied. pressure range of 0-25.,000 p.s.i. Ordinarily two ormore manifolded pressure gau.-es having varying pressure ranges will be employed inste@,id of the si-@igle gauge illustrated in order to assure high accuracy at all presstire levels. The pres- 5 Q.ure-meastiring instrument should, of course, be connected to the pressuring fliiid side Of the bellows and not to the mercury s@ 'de thereof because the measuring element itself undergoes appreciable volume change which would introduce substantial error into the overall - measurement if 10 the gaugew ere directly connected to space 2 of casing 1. Obviously, more elaborate instrumentation may be utilized if desired. For exa-mple, ;@n optical deflectometer may be used for detecting shaft displacement chan,-es of the order of 10-5 inches, and a suppressed range, narrow span pres15 sure transducer may be employed instead of the conlientiorial full ran,oe indicatin,- gau-e. One of the advantages of the present invention is that it provides a continuous analog indication (shaft displacement) of the pore volume fflled, and therefore is readily adapted for use with auto20 matic curve-dralving devices. For example, in a more refined version of this i-@ivention, an electronic displacement sensor is activated by differential transformer ineans ma,@n.-tically coupled, to shaft 13, an electronic pressure transdticer is connected to the pressuring fluid supply line, 25 and the output signals of these transducers are then fed to an X-Y recorder. The pressure output of pressure generator 30 is i@-icreased at a slow but steady rate which may be provided by a programmed rate-o'L-rise controller, and a pressure versus volume curve is automatically 3 0 plotted by the X-Y recorder. In a typical laboratory 4Dplication involvin, daily a large number of pore volume determinations, it will be advantageous to utilize a plurality of porosimeters connected in parahel, with the pressuring fluid to all of them 35 being suppl.ied from a common presstire source. Altholigli the present apparatus is designed primarily for use with mercury, it is contemplated that other penetration liquids such as carbon tetrachloride may be used therein at the option of the user. 40 The uncomplicated construction of this invention results in ease of mtnufacture and assembly, low first cost, and low mainte-@iance expense. The bellows member and the several mechanical seals are the only elements subj.--ct to wear and tear, and these are easily and quickly 45 replaced with ordinary tools. The hazard and expense of a glass viewing panel is eliminated, together with the very restrictive pressure limitations commonly associated with such type of apparatus, whil.- an accurate, reproducible means of determining volume changes is provided 50 by the bellows-shaft combination. I