det. humedad en tapones

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FIGU RE 1. Distillation apparatus.

U. The overflow tube slopes upward from theing flask. A capillary tub e, C, 56 cm long and1.5-ml volume is sealed to the bottom ofthe trap . Th is capillary isXd Y (50-cm length) and has a 12/3 ball joint atTh is joint, lubrica ted witii silicone

II , which has a drain stopcock at the bottom .P, which is in turn connected byL. The levelingboth a coarse and a fine adjustm ent. Rais-S, affords the coarseH, allows thene adjustm ent. Therm ome ter reading lenses prove

tube.The capillary tube, the trap, and the condenserdroplets from adhering to the walls of

ara tus . Th e effect of this coating is to reversethe result is ameniscus that is easily seen in theTh e silicone coating is applied by pouringmethylchlorosilanes (Dri-in) dissolved in 100 ml of dry toluene, into theair-dried apparatus and allowing it. to stand inapproximately 15 min before pouring outcess solution. I t is important that the glass-air-dry and not oven-dry, as a very thin

tial to form the coating [14]. Caution: It is recom-mended that this operation be carried out in a hood, asthe methyl chlorosilanes are toxic,flammable,an d corro-sive. The apparatus is then air-dried and heatedovernight in an oven at 105 C. The a ppa ratusmay be used indefinitely and may even be rinsedwith acid-dichromate cleaning solution without dis-turbing the film or the calibration of the capillary.However, the film may be removed by soaking theequ ipm ent for 10 to 15 min in alcoholic potass iumhydroxide.The distilling flask may be heated by any suitableheat source, but an electric enveloping heater isrecommended for best control of the distillation.

III. Operation of Apparatus1. Calibration

The capillary is calibrated by adding, progres-sively, weighed increments of water to the taperedportion of the trap, which has been filled previouslywith dry toluene up to the overflow tu l^ . Aftereach increment has been added, the water in thetrap is raised up into the graduated capillary bylowering the leveling bulb . Th e fine adjustm entaffords a simple and quick method for adjusting thebottom of the water column to a zero point on thecapillary. Th e height of the column is noted andthe leveling bulb raised to return the water to thetapered portion of the tra p. An other weighed incre-ment of water is added and the process repeated.The size and number of the increments to be meas-ured depends on the accuracy and precision desired.Because toluene is present in the t rap, the watercolumn is confined between two columns of toluenewhile being measured. This prevents evaporationloss and also aids in obtaining a sharp mercury-typemeniscus at bot h ends of the wa ter column. Va ryingthe weight of the water added and measuring thecolumn leng ths obtaine d allows precise calibration ofthe capillary. If the capillary is uniform, a simplelength-to-weight factor is all th at is required. How -ever, if the capillary is nonuniform, a simple graph-ical calibration curve is readily made from suchmeasurements.

2. Distillation of SampleThe sample is weighed to the desired accuracy andplaced in the distilling flask with a sufficient amountof toluene to keep the sample covered. The tolueneis dried by passing it through a column of activated

silica gel. Th e tra p is filled up to the overflow tu bewith dry toluene and the distilling flask heatedslowly until Liquid begins to drop from the tip of thecondenser. The distillation is continued at theproper rate, depending on the type of sample used,until no more water droplets appear in the distillatedropping into the large pa rt of the tra p. Five milli-liters of dry toluene is poured in the top of the con-denser to wash any water adhering to the condenserdown into the trap . The heater is then turned offand the water in the trap allowed to cool to room363


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temperature, or a beaker with cool water may belifted around the trap to aid in adjusting the temper-ature to a predetermined value, dependent on thetem per atu re of the calibration procedure. Aftercooling, the leveling bulb is lowered to draw thedistilled water into the capillary and to adjust thebottom of the water column to the zero point usedas a reference in the calibration of the graduatedcapillary. Th e length of the water column is read,and then the leveling bulb is lowered further todraw the water and toluene in the trap into thewa ste receiver. Th e trap is again filled up to theoverflow tube with dry toluene, and the distillingflask is replaced with another flask containing asample and toluene. This procedure allows anoth ersample to be run almost imm ediately. Cleaning thetrap at intervals by flushing with toluene is accom-plished by pouring toluene in the trap through thecondenser and lowering the leveling bulb to drawthe solvent through the capillary into the wastereceiver. Th e stopcock on the bottom of the was tereceiver allows removal of the accumulation of waterand tolufne.

IV . Accuracy and PrecisionSeveral experiments, designed for statistical analy-sis, in which a number of possible variables werestudied, were used to evaluate the me thod. Theknown samples were prepared in batches by taking a200-g batch of GR -S-1 0 sy nthetic rubber and m illingit for approximately 5 min., after w hich it was sheetedout at a setting of 0.02-in. distance between themill rolls and then placed in a vacuum oven at 90 Cfor 4 hrs . After the rubber was dried, it was storedin a desiccator overnight. The rubber was thenweighed to the nearest milligram and passed throughthe m ill at a 0.02-in. setting several times, takin g care

tha t no rubb er was lost from the mill. Th e samplewas reweighed to check for loss of rub be r. Afterth e rubber was checked for loss in weight, it wasbanded on the mill, and two 10-ml portions of dis-tilled water were milled into the sample and the mix-ture thoroughly blended. The sample was next re-moved from the mill and placed on an electricallygrounded sheet of aluminum to cool and discharge th estatic charge formed during the milling operation.A f t e r a p p r o x i m a t e l y 1 0 m i n . , t h e r u b b e r w a s w e i g h e d .A p o r t i o n o f t h e r u b b e r was cu t i n t o p i eces s m a l le n o u g h ( o pa s s thro ug h t h e o p en i n g o f (h e di s t i l l i ngf l ask and p laced a s qu i ck l y as poss ib le in a. w eig he dt i n w i t h an air-tigh1 c o v e r . T h e r e m a i n i n g p o r t i o no f t h e we t rubber w a s rew e i g hed an d s t o red in an air-t i g h t c o n t a i n e r . T h e tin . c o n t a i n i n g t h e s a m p l e w a sw e i g h e d a n d t h e s a m p l e t h e n r e m o v e d a n d p l a c e din the flask c o n t a i n i n g t h e t o l u e n e . T h i s pro ceduregave several checks for t h(moisture content, by Weig]moisture during handlingthe loss of moisture duringl ess than . I mg.T h e d a t a s h o w n i n ta b l ea n a l y s i s , i nd i ca ted t h a t t h e n

Weight o f t h e s a m p l e , t h e, an d t h e poss ible loss ofU n d e r t h e s e c o n d i t i o n sh a n d l i n g was fo u n d t o h e

pendence of the precision and accuracy, within thlimits of this experiment, on the size of the sampor on the time of distillation after the water droplecease to appe ar in the distillate. Th e slope and intecept of each curve shown in figures 2,3, and 4 indica

3 4 5 6 7 8 9 10 II 12AMOUNT OF WATER ADDED,GRAMS

13 14 FIGURE 2. Amount of water recovered versus the amount water added for untreated drum toluene used directly.

O, 45-min distillation; , 90-min distillation; 120-rnin distillation. Intcept, 0.070 g; slope, 1.03.

- 1 0 -

3 4 5 6 7 8 9 10 II 12AMOUNT OF WATER ADDED.GRAMS

13 14

was no siafter statisticaln i l i can l d e -

FlGURB -5. A in-min distillatio n; I I, 90-min d istillation; . L20-min dist illati on! Intcept, 0.028 n; slope, 0.1157.

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3 4 5 6 7 8 9 10AMOUNT OF WATER ADDED, GRAMS

II 12 13 14 15

4. Amount of water recovered versus the amount ofwater added for drum toluene distilled and the wet forerunremoved., 45-min distillation; , 90-min distillation; #120-m in distillation. Inter-t, 0.085 g; slope, 0.986.

and correction for water in each of thein table 1. The toluene treated withbut also showed no significant water correc-on for the toluene. T ha t the other toluenes did nota significant difference from 100-percent re-probably du e to the lower precision in thesethe water correction was appre-for these two toluenes. Fur ther, the toluene

gel gave the lowest standardof the three toluenes.1. Standard deviation, water correction, and recoveryas affected by treatment of the toluene

(g) 11

.3488

.8064. 7289

. 3 1 6 68061

W e i g h t orw : i l e r re-coveredgI. 13390. 4650. 6058. 7703.3714

8 3 5 7. 7053. 3316. 7628

i). 02:!. 028295. 66

1 ( i s t i l l ed to lu en e

W e i g h i ofw a t e r inru b b er

g1). 96961. 28660 3327. . r > i ; . r > (i. 1285

. 9839. 4896. 9737. 3887

W e i g h i ofw a t e r re-covered

g0 . 98881. 10710. 3865. 6070

. 52311.048811 59281 0135n. 1878

0 . 035. 084998 63

Untreated toluene

Weight ofwater inrubberg0.4847. 8672

. 9008. 2601.69911 2306(i 2598. 64221. HIM

Weigh t "i a ter re-coveredg

0. 5743. 9748I.0S210. 3564. 75861 29470 .3 1 5 9. 70691.2188

0. m o1704103.01

Comparisons were also made between this methodand those involving the mastication of the sampleson hot rolls or oven-drying of thin sheets. Thedata from such a comparison is shown in table 2.The weights of sample used for the water determi-nation in the four methods were quite different,ranging from a fewgrams for the Mill-oven methodto 450 g for the hot-mill me thod. How ever, a com-parison of the standard deviations of the methodsindicates that the distillation method ismore precisethan either the Goodrich method or the SpecificationHot-mi l l method. The Specification Mill-ovenmethod is more precise than the distillation method,but the operating factors of the mill method are toits disadvantage [12].T A B L E 2. Comparison of methods for the determination ofmoisture in synthetic rubbers

Method.

DistillationSpecification Mill-oven Method (C- l-c)[12]Specification Hot-mill Method (C-l-a)[12]Goodrich [12, 13]

Toluenet r ea tment

(Silica geL-^ D ist i l l ed - .(.Untreated-

Standard devi-ation of a singledeterminat ionof waterPercent0.023.035.040

.045.0 5

Single determinai [on.

The author is very grateful to Patricia CusterJackson and Aurelia Arnold for making numerousmeasurements for the purpose of evaluating the im-provements in the apparatus, and also to JohnMandel for advice and assistance in designing sta-tistical experiments to show quantitatively the valueof the improvements.V. References

[1] E. W. Dean and D. D. Stark, A convenient method forth e determination of water in petroleum and otherorganic emulsions, Ind. Eng. ('hem. 12, 480 (1920).[2] G. L. Bidwell and W. V. Sterl ing, Preliminary notes onthe direct determination of moisture, End. Eng, ('hem.1 7 , 147 ( 1925 ) .[3 ] .). A. DeLoureiro, An improved technic in the toluenedistillation method Tor the determination of moisturein food s! nil's, .1. A.8SOC. Official Agr. ('hem. 21, 645( 1938 ) .[4 ] .). K. Cleland and YV U. Fetzer, Determination ofmoisture in sugar products , Ind. Eng. ('hem. Anal .Ed . 14, 12 1 (1942) .[5 ] W. (!. Marskell an d J. E. Etayner, An improved apparatusf o r t he d e t e r m i n a t i o n of w a t e r in o i l s a n d f u e l s , F u e l2 , 49 (1947).| ( ) | \ Y. X o r m a n n , Z u r w a s s e r b e s ! i n i i n u n i ; in f e t l e n u n danderen stoffen, Z. angew. C h e m . 38, 380 (l(.)2.r>).|7 | A. ('. Beckel, A. G. S h a r p , and 1!. T. Milner, Apparatusfor determining moisture by the distillation m e t h o d ,I nd . Eng. Chem. Ana l . Ed. 11, 425 ( 1939 ) .[8] I1'.. I!. Caley and L. G ordon , Trap for the determination

o f w a t e r by t h e d i s t i l l a t i o n m e t h o d , A n a l . C h e m . 2 1 ,7 4 9 (\\\)).|U | ,1. Mitchell and I >. M. S m i t h , Aquametry, pp. I to 5( I n t e r s c i e n c e P u b l i s h e r s , I n c . , N e w Y o r k , X . Y . , I ( . ) I S ) .| K ) | M. T r y o n and I'. Custer, National Bureau of S t a n d a r d s ,unpublished repori to Office of Rubber Reserve (May24, L948).

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[11] M. Tryon , P. C. Jackson, an d J. Ma ndel, N ation alBureau of Standards, unpublished report to Office ofRubber Reserve (Feb. 28, 1949).[12] P. Custer, National Bureau of Standards, unpublishedreport to Office of Rubber Reserve (Feb. 6, 1947).[13] P. C. Baker, B. F. Goodrich Chemical Co., unpublishedreport to Office of Rubber Reserve (Aug. 20, 1946).

[14] E. G. Rochow, Introduction to the c hem istry of tsilicones, p. 32 an d 83 to 88 (John Wiley an d SonInc., New York, N. Y., 1946).

W A S H I N G T O N , January 24, 1950.

Journal of Research of the National Bureau of Standards Vol. 45, No. 5, November 1950 Research Paper 21

Porcelains Within the Beryllia Field of the SystemBeryllia-Alumina-ZirconiaBy Stewart M. Lang, Laurel H. Maxwell, and Milton D. Burdick

The general physical properties of practically impervious porcelains within the beryllia(BeO) field of the system beryllia-alumina-zirconia (BeO-Al2O3-ZrO2), whose base composi-t ions approximate that of NBS Body No. 4811C, were found to be: maturing range, 1,500to 1,600 C; apparent density, 2.9 to 3.4 g/cm 3; shrinkage, 17.8 to 20.5 percent; room-temperature compressive strength, 238,000 to 305,000 lb/in.2; room-temperature t ransversestrength, 17,200 to 34,100 lb/in.2 ; room-temperature t ransverse s trength after thermalshocking, 17,800 to 31,900 lb/in.2; t ransverse s trength at 1,800 F (982 C), 15,100 to 25,100lb/in.2; approximate Young's modulus at 1,800 F, 28,000,000 to 38,000,000 lb/in.2 ; relativether ma l shock resistance, good; and K noop hardness numb ers (500-g load), 550 to 830. Anadmixture of 2 weight percent of calcia (CaO) to the base compositions of these porcelains(without which the specimens would not mature to an impervious structure) caused theappearance of unidentified isotropic phases.

I. IntroductionBecause o f t he advan t ageous h i gh - t em per a t u r est rength character ist ics of "glass- f ree" bodies com-posed of the ceramic oxides, singly or in combinat ion,as compared to s imi lar s t r ength proper t i es of themeta l l i c a l loys , many ref r ac tory porce la ins may bepa r t icu lar ly wel l ad ap ted for diversi fied use s in suchpower -p lant s as the gas- turb ine and j e t -propul s ionengines .Previous wo rk at this Bu rea u [1, 2, 3] ,1 at theOhio Sta t e U niver s i ty Ex per im ent S ta t ion [4], a t t heU niversity- of I l l inois [5], and at t he Lew is Flig htP r opu l s i on Labor a t o r y o f t he N a t i ona l A d i vso r yCo mm i t t ee for Aero naut i cs [6] has shown N B S B odyNo. 481 lC [3] , who se comp osi t ion is wi th in thesys t em berylUa-alumina-zirconia ( BeO - A l2 ( V ZK ) 2 ) ,t o be ou t s t and i ng i n m any high-temperature prop-erties when compared with o t he r refractory white-wares. Such comparisons made it seem advisableto investigate and report some of the physicalproperties of porcelains whose composi t ions approxi-mate that of body 481 LC.A previous repo rt [3] give s in som e detail (lie phaserelations of (he system Be()-AI,,().;-Zr().,. The failureof t hese oxide bodies to mature to nonporous s t ruc-tures was discussed in the Bureau report, but it wasshown that th e addition of small quantities ofauxiliary (luxes to the base composi t ions did permitmatur ing of the bodies to a, practically imperviouscon di t ion. An add i t ion of 4 percent of magensia, tob o d y 4 8 1 1 , whose mole composi t ion rat io i s 48BeO: 1ALO..,: l/i() 2 , caused the most p ronouncedFigu res in l . racke t s Indica te the l i t e ra tu re re fe rences ;i i t he end of th i s pap er .

effect on the m atur ing r ange . Exp er i ence has showth at th e use of magn es ia t ends to increase the pa r t i cs i zes or d i s tor t t he par t i c l e shapes and thereby tdecrease the bod y s t r eng th . Consider ing al l of thproper t i es s tudied , an add i t ion of 2 weight perc enof calcia (CaO) produced the most sat isfactory 481bodies , and th i s par t i cu lar body composi t ion i s correc t ly des ignated as Bo dy No . 4811C . Al l bu t onof the porcelain composi t ions given in this reporcontain a 2-percent addi t ion of calcia to the bascomposi t ion; the except ion , for compara t ive puposes, i s body 4811M, which conta ins an addi t ion o4 percent of magnes ia .

II. Materials and EquipmentThe oxides used in the preparation of the tesspecimens were commercia l ly avai l ab le mater i a l s ohigh pu r i ty. Th e beryll ia (BeO) was of nom ina99.7-percent purity, and spectrograms showed onlt races of copper , iron, and magnes ium , and verweak lines of silicon. Ground, washed, and sievetabular alumina (AI2O3) of 99.5-percent pur i t y w asupplied through the cour tesy of the Champio

Spark Plug C o. Commercial zi rconia (Zr( )2) onominal 99-percent purity was recalcined a t 1,4-40C , a f t e r wh i ch s p e c t r o g r a m s s h o w e d m e d i u m l i n efo r n i o b i u m ( c o l u m b i u m ) a n d t i t a n i u m , a n d o n lvery weak l i n es o r t r ace s fo r c a l c i u m , c o p p e r , i ro nm a g n e s i u m , l e a d , an d s i l i co n . C a l c i a ( C a O ) w aadded as (he pure chemical ly precipi tated carbonateAs prepared for use, the ma teri als were , in all ins t ances , sufficiently finely div ided to pass the N o;!2r> [] . S. S tand ard Sieve. Com minu t ion procedu rehave been given [7].366

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