calculation of the compounds in portland cement

8/12/2019 Calculation of the Compounds in Portland Cement

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192 A N A L Y T I C A L EDITION Vol. 1,No. 4

hand, care must be taken not to bake the residue and thusdecompose the calcium chloride, since in th at case it will notbe possible to obta in a clear solution in water . A safer pro-cedure is to finish the evaporation over a water bath. Forextensive manipulative no tes on the remainder of the m ethodthe reader is referred to th e recent paper on the direct mag-nesium-uranyl acetate method for sodium I ) . No diffi-culties will be encountered, however, if the details as givenabove a re followed.

Results

The average results obtained on several representativesamples of reagent-grade calcium carbonate by both the oldand new methods are shown in Table I. In each case theactual sodium in the extraction residue was determined bythe new method in order to ascertain the actual amount ofalkali extracted from the samples by boiling with distilledwater.

From the data shown in the table it is obvious that theextraction method gives neither true nor comparative resultsfor the alkali content of reagent-grade calcium carbonate.The m inute am ounts of sodium found in the residue obtainedby ev aporating the w ater extract d emonstrate clearly the

futi lity of a ttem pting to remove and determine adsorbedalkali salts by a washing process. The residues obtained byextraction consist chiefly of calcium carbonate dissolved bythe relatively large volume of w ater used in the meth od.

Th e results also show tha t ther e is a considerable varia tionin the sodium co nte nt of th e samples of reage nt-grade calciumcarb onate from different sources, although the usual m ethodof testing the material would not indicate this variation.

Table I -Comparative Resul ts in Determinat ion of S o d i u m inSamples of Reagent Calc ium Ca rbonate by Ext r act ion Method an d

by Magnesium-Uranyl Acetate Metho d

SODIUM ALKALI SODIUMALKALI CONTENT CON- ACTUALLY

CONTENT SODIUM C AI.Cn. TENT PRESENT I N

LABEL CONTENT TO EXTRAC- XTRAC-STATE- NEW CARBON- TION TION

Per cent Pe r cen Pe r cent Per cent Pdr cent

SAMPLE MENT METHOD ATE METHOD RE31DUEa

Stan dard stock material None 0.13 0.30 0.02 0 .002Standard stock material . 0 . 0 5 0 . 1 2 0 . 2 8 0 . 0 2 0.003

Specially prepared lot Low 0 . 0 2 0.05 0 . 0 4 0 , 0 0 1Standard stock material 0 . 0 1 0.008 0 . 0 1 8 0.01 < 0 . 0 0 1Selected lot from standar d

stock material 0 . 0 5 3 0 .006 0.014 0 .01 < 0 . 0 0 1

a Expresse d in percentag e of sample take n.

It was found, also, that the magnesium-uranyl acetatemethod gave results for the sodium conten t of this chemicalin a shorter time th an the usual extraction procedure.

I n conclusion, it may be sta ted t ha t this new met)od fordetermining small amounts of sodium is applicable to a wideran ge of chem icals inte nde d for reage nt purposes, especiallythose of th e alkali and alk aline ea rth groups, a nd even ofman y of the heavy metals as well. I n many of these casesthe method as outlined above is quite suitable, but in someother cases certa in modifications are necessary. Inves tiga-tions in regard to these modifications are being pursued and itis intended to publish the findings late r.

Literature Cited

1 ) Caley and Foulk, J . A m . Chem. Soc. , 61, 1664 1929) .

2) Hillebrand, U . Geol. Survey, Bull . 700 208 1929).

(3) Murray, "Standards and Tests for Reagent and C. P. Chemicals,"

(4) Singleton and Williams, Analys t , 47, 252 1922) .

p. 179, D. Van Nostrand Co., 1927.

Calculation of the Compounds in Portland CementR . H . Bogue

PORTLAND CEMENT ASSOCIATIONELLOWSHIP,UREAU F STANDARDS, WASHINGTON,. C.

In addition to the five com-combinat ions of the in Portland cement from chemical analyses are pre- ponents listed above, corn-S omponents CaO, MgO, sented. Arithmetical and diagrammatical methods are mercia l Por t l and cements

A1&, Fe2O3, an d SiOz ha ve given for such a calculation. compounds con- con ta in smal l am o u n t s o fbeen studied and reported by sidered are ~C~O.A~ZOS.F~ZO~,Ca0.A120a1 2CaO.Si0z1 other materials in variablethis and other laboratories 3Ca0.Si0z1 um~ mb in edMgO, uncombined CaO, and quantity. These may include3, 5 , 7 , 8, 10, 11). It has CaS04. Other components than those included in soda, potash, titania,m anga-

been found that when these these compounds are not at Present Considered as their nese oxides, phosphates, andcom po ne nt s ar e i n t i m a t e l y forms of combination are not known. perhaps still other materials.mixed in proportions similar The tota l amo unt of theseto those found in Po rtland cements, and burned to equilib- lesser components, however, probably does not often exceedrium, the following compounds are formed: 4Ca0.A1203.Fez03, 2 per cent.3Ca0.A1203,2Ca0 .Si02, 3Ca0.Si02, and M gO. Th e manner of co mbina tion of these lesser components is

Note-In a former publication 6) t was reported that MgO enters into not known. It is possible tha t some of them, as perhaps th e

Y S T E M S c o n t a i n i n g The bases for a calculation of the compounds present

solid solution with 4CaO.AlzO~.FezO3,he end member of the series being

4Ca0.2MgO.AIzOa.FezO~. Magnesia in excess of tha t required for the above

combination was found to remain as uncombined MgO. More recent in-

formation obtained in this laboratory indicates that the amount of the solid

there is no reasonable doubt that a large part of the magnesia remains

uncombined, the exact natu re and degree of th e reaction by which the

4CaO.AlzOa.FezOa is chang ed in color a nd pleochroism in th e presence of a

small amount of magnesia has not been determined. This problem is under

furthe r investigation. At present the magnesia may be considered as re-

maining essentially uncombined, and the iron compound as existing essen-

tially in the form of 4CaO.AhOa FezOs.

alkalies, may have a significant influence on the relativeamounts Of the major that are formed, but sincethe IT le r of their combination is not yet known, the effects

it is not possible at present to consider those components inthe calculation Of cement constitution'

It is assumed that the compounds Of Portland cement areessentially the same as those of the pure five-component

solution is much smaller than had p reviously been reported Although of their presence cannot now be evalua ted. Consequently,

system given above when the components are present in theproportions found in commercial cements. Th e general

correctness of this assumption has been confirmed by informa-

tion obta ined from cooling curves 41, from microscopic exami-nations I ) and f rom x-ray diffraction photographs 1 ) .

1 Received June 17, 1929. Publication approved by the Director of

NO. 21 of the Portland Cement Association Fellowship a t the Bureau of

Standards.

the National Bureau of Standards, U. S. Depdrtment of Commerce, Paper



October 15, 1929 I N DU S TRI AL AN D EN GIN EERIN G C HEMI S TRY 193

M a n n e r of Reaction

The manner in which the components react determines therelative am ounts of the resulting compounds. Infor mati onobtained at this laboratory leads to the following generaliza-tions:

(1) The ferric oxide reacts with alumina and lime to form4CaO.Al203.FezOa. (See note .)

(2) The magnesia remains essentially in the form of uncom-bined MgO.

(3) The alumina remaining from combination as 4Ca 0.-A1203,Fe203eacts with lime to form 3CaO.Al203.

(4) The lime remaining from the above combinations reactswith the silica. The compound 2Ca 0.Si 02 is formed, and anyCaO then uncombined reacts with the 2CaO.SiO2 to form3CaO.SiOg. If CaO remains after converting all of the 2Ca 0.Si 02to 3CaO.SiO2, it w ill be present a s uncombined C aO.

The formation of t he compounds as described assumes tha ta cond ition of equilibrium has been reached dur ing the prog-ress of the reactions in the kiln, A small amo unt of uncom-bined CaO m ay remain in the clinker, however, indicating (ifthe composition is such that the CaO would be completelycombined a t equilibrium) tha t th e reactions are not altogethercomplete. This departur e from complete combination is not

usually of suficient magnitude to produce a change in thenatur e of the compounds formed, but it does produce a changein the relative amo unts of the compounds produced. For tha treason it is important that free CaO in the cement be de-termined (9) and th at the amount present be taken into con-sideration in the calculation of th e constitution. If this isnot done, an e rror of usually small but uncertain m agnitudemay be introduced.

The “insoluble residue” obtained in a cement analysis iscomposed of q uar tz, titan ia, an d several other materials.Th e am ount of the residue is usually very small, abou t 0.2per cent. Because of the low qua ntity of this ma terial andthe variable a nd unce rtain natu re of its composition, it seemsinexpedient to atte mp t t o introduce a correction factor for it.I n unusual cases where the amo unt of t he residue is high, it

ma y be desirable to analyze it to ascertain if an appreciablequa ntity of silica has remained as free quartz . If the residueis found t o contain an appreciable amou nt of silica, then th esilica content of t he residue should be deducted from th etotal S i02 o obtain the value of the SiOz taking pa rt in th ereactions.

Th e “ignition loss” consists essentia lly of mo isture an d car-bon dioxide tha t have been take n up by the cement followingthe burning operation. I n calculating the constitution, thisvalue is accordingly set down without further change.

By means of t he information given above, the relativeam ounts of th e compounds present in Portland cem ent orclinker may be calculated from the chemical analyses. It isessential in a ny case to consider the So3 content an d calculatetha t to CaS04.

Accuracy of C o m p u t a t i o n s

The accurac y of the com putations depends on the correct-ness of both the postulations and the analytical values. Thepostulations as given represent t he best available information,but are subject to revision and extension as has been pointedout. The general correctness of th e analytical values willvary with the conditions of test and the personal facto r. I nany case it is not recommended that analyses be consideredas accu rate beyond th e first decimal place.

An examination. of the facto rs given below will show tha terrors of analysis often a re magnified in the com putations forcompound composition. Thu s a plus error (other values re-maining fixed) of 0.2 per cent CaO or uncombined CaO (ex-pressed as percentag e of t he cem ent) will increase the com-puted 3Ca0.S i02 about 0.8 per cent and decrease the com-

puted 2CaO.Si02 about 0.6 per cent. A plus error of 0.2 percent F e20 3 will increase the computed 4Ca 0.A1203.F e203about 0 6 per cent, decrease the 3Ca0.A1203about 0.3 percent, decrease the 3Ca0 .Si02 about 0.3 per ce nt, and increasethe 2CaO.Si02 about 0.2 per cent. A plus error of 0.2 percent A1203 will increase th e c omp uted 3CaO .Al203 abo ut 0 .5per cen t, decrease the 3CaO.Si02 abou t 1 .3 per ce nt, and in-

crease the 2Ca0 .Si02 about 1.0 per cent. A plus error of 0 2per cent Si02will decrease the com puted 3CaO.Si02 about 1.5

per cent and increase the 2CaO.Si02, 1.3 per cent. Fo r thesereasons only analytical data that are believed to be reliableshould be employed for the co mpu tation of compound com-position, an d an expression of t he com pounds 4CaO.AI2O3.-Fe203,3CaO.Al203, 3Ca 0.Si02, and 2C a0.S i02 should not begiven to a closer approximation than the nearest whole num-ber.

Method of Calculat ion

Each per cent of So3 enters into combination with 0.70per cent CaO to form 1.70 per cent CaS04:

CaO - 56.07

SOa= 0 .70 per cent CaO. . . . . . . . .

Eac h per cent of F e2 03 nter s into combination with 0.64per cent A1203:

Fen03 - 159.6801’92 - 0.64 per cent A1203.. . . .

and w ith 1.40 per cent CaO:

4Ca0_ - = 224.281.40 per cent C aO .. . . . . . . . . . .

Fen08 159.68

to form 3.04 per cent 4CaO.Al20Jh203.The total M gO is recorded as uncombined MgO.Th e t ota l A1203 minus al) ives th e A1203 az) available for

combination as 3Ca0.A 1203. Ea ch per cent of a2) will enterinto com bination with 1.65 per cent CaO t o form 2.65 percent 3CaO.Al203:

- - - =Ca0 - 168’211.65 per cent CaO. . . . . . . . . 63)

A1203 101.92The a mou nt of C aO available for combination with SiOz

is obtained by subtracting from th e to tal CaO the sum of th euncombined CaO, the CaO cl) combined as CaS04, the CaOcz) combined as 4Ca0.Al2O3.Fe203,and the CaO 4 om-

bined as 3CaO.Al203:Total CaO - uncombined CaO + c1 + c2 + 63) =

CaO available to combine with SiO2. . . . c)

The tota l Si 02 (s), unless corrected for silica in the “insolu-ble residue,” is calculated first to combine with CaO tofor m 2C a0.S i02 . Eac h per cent of Si02 (s) will combine withCaO to form 2.87 per cent 2CaO.SiOz:

This first approximation to the value of 2Ca 0.Si02 is sub-

tracted from the Si02 (s) + CaO e ) , which gives the CaOc4) available to combine with 2CaO.Si02 to form 3Ca0.Si02.

Ea ch per cent of CaO cq) combines with 2Ca0.S i02 o form4.07 per cent 3CaO.SiO2:

3Ca0’Si02 _ _ _ _228*27= 4. 07 per cent 3CaO.SiO2CaO 56.07

The 3Ca0 .Si02 subtracted from the total Si02 (s) + CaO

If the computed 3Ca0.SiOz is greater th an s + e, no 2Ca0.-I n tha t case each per cent of S i02 (s) com-

(c) gives the true amo unt of 2CaO.Si02 present..

Si02 s present.bines with CaO to form 3.80 per cent 3CaO.SiO2:

This am ount of 3Ca 0.S i02 subtr acted from Si02 (s) CaO(c) gives the percentage of uncombined CaO. Th e above



194 A N A L Y T I C A L E D IT IO N VOl. 1 No. 4

A L2 '+

Y

b

Application of the Methodcondition can obtain only when the lime is in excess of t h a twhich can go into combination a t equilibrium, an d the un-combined CaO has not been determined and deducted as pre-\TiousIy de scribed.

A diagrammatic method for obtaining these relationsbeen found useful in computing the a mou nts of the cornpoifrom chemical analyses. Such a method has not th e preci

i has

indaision



196 ANALYT ICAL EDITION Vol. 1, N o. 4

In this case only, both readings are taken from the horizontalaxis. It is desired to find the CaO equivalent of 2.0 SO8 in theform ation of CaS0 4. The point 2.0 on the horizo ntal axis of t helower diagram in Figure 1 is followed upward on the verticalcoordinate until it intercepts the radial line for SO8. The di-agonal coordinate is then followed until the radial line for CaOis intercepted , The vertical coordinate is again followed downfrom tha t point to t he horizontal axis, and the value 1.4 obtained.

The value read, 1.4, is placed at c1 and th e sum of th e two,3.4, is placed a t the bottom.of the column under “CaS04.”

The value for Fe203, 3.4, is transferred to the “Fe203 q.”column and the A1203 nd CaO equivalent to the Fez03 eadfrom the lower diagram in Figure 1.

It is desired in thi s case to find the Also8and CaO equivalentsof 3.4 Fe z08 n the formation of 4C a0.AlzOa.Fe203. The point3.4on the ver tical axis of t he lower diagram in Figure 1 s followedon the diagonal coordinate until it intercepts the radial line forAl&. The vertical coordinate is then followed down from th atpoint and the value 2.2 A1203 ead off on the horizontal axis.The point 3.4 on the vertical axis is again followed on the di-agonal coordinate until it intercepts the radial line for CaO.Again the vertical coordinate is followed downward and the value4.8 CaO read off on the horizontal axis.

The values as read are placed in the column a t their proper

places: Thethree figures in the column a re now added to give the 4Ca0.-A1203.Fe203. This value to the nearest whole number isplaced at the base of the column. The amo unt also ma y beread directly from th e diagram if desired.

the AlZO3, .2, a t al; and the CaO, 4.8, a t c2.

Ta bl e I- C ha r t U s e d f o r R e c o r d i ng S i g n i f i c a nt D a t a in C o m p u t a t i o no f C o m p o u n d s

COMPONENTS

1 . 1 3 . 7 1 0 . 3 3 . 4 I 10 I 6 I 44 31

The value al, 2.2, is subtracted from A1203, 4.5, to give az,

2.3, the A1203available to combine as 3CaO.Al2O3,which isplaced in the “A1203 q.” column a t a2 The CaO equivalentof this, 3.8, is read from th e upper diagram of F igure 1 andplaced at c3. The two values are added t o give the 3Ca0 .-A1203 and th at figure to the nearest whole number broughtto the foot of the column. This value also ma y be read di-rectly if desired.

The CaO, c, available for combination with the silica isnow found by subtracting from the total CaO the free CaO,c, c2, and c3: 62.8 - 0.3 + 1.4 + 4.8 + 3.8) = 52.5whichis set down at c . The tota l SiOz, 22.3 (unless corrected for

the quartz in th e insoluble residue) is set down at s.The computed tricalcium silicate and dicalcium silicate

are now read directly from the diagram a ) in Figure 2.Th e point is found which is the intersection of the ve rticalcoordinate representing S i02 (s) and the horizontal coordinaterepresenting the CaO (c) available for combination with thesilica. Th e 3CaO.Si02 corresponding to this point, 44 percent, is read to the nearest whole number on the diagonalcoordinate that is parallel to the lower right base line, asindicated. Th e 2CaO.SiO2, 31 per cent, is read on the diag-onal coordinate that is parallel to the upper left base line, asindicated. These values are set down in the lower row ofcompounds unde r C3S and CzS, respectively.

In th e event t ha t the point represented by the intersectionof the coordinates for CaO an d Si02 lies to th e left of the

diagram, there is present an excess of lime above th at required

to convert all of the 2CaO.SiO2 to 3CaO.Si02. I n tha t casethere is some uncombined CaO presen t a nd no dicalcium sili-cate. The tricalcium silicate content is found by reading thatvalue a t the point where the SiOz coordinate intersects theupper left boundary of the figure. The lime required for tha tcompound is then read off on the CaO (horizontal) coordinateand the remaining lime is uncombined. Fo r example, con-

sider th at c = 59.0 and s = 20.5. Th e Si02 coordinate cuts theupper boundary at a point represented by about 78 per cent3Ca 0.Si0 2. The CaO required is read to be 57.5 per cent.The free CaO is then 1.5 per cent. Such a value should be re-corded in the “free CaO ” column opposite SiOz and br ough tto th e lower row of compounds.

The upper right boundary curve as drawn represents thecompositions a t which the su m of t he two calcium silicates is80 per cent. Th e remaining ma teria l includes all othe r com-pounds-as 3CaO.AI203, 4CaO.Al203.Fez03, Mg O, alk alie s,free CaO if present, CaS04, and any othe r constituents. Th elower left bounda ry curve as drawn represents the composi-tions a t which the sum of t he tw o silicates is 65 per cent, theremaining 35 per cent being the other compounds as above.It is probable that most commercial cements fall within these

limits, but t he diagram m ay be extended up to the line repre-senting 100 per cent 2CaO.Si02 plus 3CaO.Si02, and downas far as desired. The upper left boundary is the line forzero 2CaO.Si02 and th e lower right bound ary is cut a t 20 percent 3CaO .Si02 since Portlan d cem ents will scarcely be foundwith less th an th at a mo unt of t he tribasic silicate. If de-sired, however, the diagram may be extended to the lowerright to zero 3CaO.Si02.

The data necessary to construct the diagrams in Figure 1are obtainable from the factors previously given. Th e fol-lowing locations of t he exter nal angles of th e diagr am in Fig-ure 2 will define th e position of t h a t figure.

LRFT TOP RIGHT R O T T O M

C a O 4 8 .6 4 5s. 5 5 3 . 8 1 4 4 . 7 0SiOa 1 7 . 3 6 2 1 . 0 5 2 6 . 1 9 2 1 . 3 0

The diagrams mus t be prepared w ith the highest precision andshould be drawn to such a scale th at estimates m ay properlybe made to 1 per cent.

There now appear on the bottom row of th e ch art the valuesfor all of th e compounds which we are able a t present t o cal-culate from the chemical analysis of a cement.

The use of facto rs in th e calculation gives values differingbu t slightly from those obtained b y the use of th e diagrams.This is brought o ut in Table 11,in which are shown the valuesobtained by factors an d by t he diagrams from the compositionrepresented by the analysis given. In this case, in order todemonstrate the difference, the values are expressed to thefirst decimal place.

T a b l e 1 1- C o m pa r is o n o f C o m p u t a t i o n s b y F a ct o r s a n d b y D i a g r a m

BY BY

COMPONE NTS ANALYSIS COMPOU NDS D I A G R A M

Per cent I Per cent P e r cent

C a O 6 2 . 8MgO 3 . 7AlzOa 4 . 5F ez 03 3 . 4Si02 2 2 . 3so3 2 . 0Igni t ion loss 1 . 1

~~

Insoluble’” 0 . 1F re e C aO a 0 . 3

T o t a l 9 9 . 8

3 Ca O .S iO a 4 4 .4 4 4 .42 Ca O.Si Oz 3 0 .5 3 0 .63 Ca O.A hO s 6 . 1 6 . 14CaO.AlzOs.Fea03 10 .3 10 .4Free MzO 3 . 7 3 . 7

0 . 3 0 . 3r e e C a bC a s0 4 3 . 4 3 . 4

1 . 1 1 . 1gnition loss

9 9 . 8 1 0 0 . 0

a Not included in total .

Literature Cited

1) Brownmiller, Paper in preparation,2) Griin and Kunze, Zemen t , 17, 1166 1928); Concrete, -34, 115 1929) ,

used a diagram of similar coardinates.

3 ) Hansen, J . A m . Chem. Soc. , SO 2155 1928).



October 15, 1929 INDUX TR IA L A ND E NGINEE R ING CHE MIX TR Y 197

4) Hansen, Paper in preparation.

( 5 ) Hansen and Bogue, J Am. Chem. Soc., 48, 1261 (1928).

6) Hansen and Brownmiller, 4 m . J Sci. 10,225 (1928).

(7) Hansen, Brownmiller, and Bogue, J Am. Ckem. Soc., 60, 396 (1928).

(8) Hansen, Dyckerhoff, Ashton, and Bogue, J P h y s . Chem. 31 607 (1927).

(9) Lerch and Bogue, IND.ND. HEM.,13 39 (1926).

( lo) Rankin and Merwin, Am J c i . , 46, 301 (1918).

11) Rankin and Wright, I b i d . , 39, 1 (1915).

Determination of the Sulfur Content of Gases fromBoiler Furnaces S 2

Edmund Tay lo r and H. F. Johns tone

PITTSBURGHXPERIMENTTATION, . S. BUREAU F MINES, PITTSBURGH,A., AND UNIVERSITYF ILLINOISNGINEERINGXPERIMENTTATION,

URBANA,LL.

The fo rm and the quan t i ty in which su l fu r exi s ts in theproducts o f combus t ion are impor tan t in connect ionwi th the i r ac t ion on t he re f rac to r ies of the fu rn ace , themet al of preheaters , economizers , and s teel s tacks, andwi th the ac ids and gases emi t ted f rom the s tack . Theeq u il i br i u m eq u a t i o n s h o ws t h a t a t f u rn ace t em p e ra t u re sthe sulfur wil l be presen t as SOz a n d t h a t SO3 will beformed as th e gases cool .

Appara tus and methods are descr ibed fo r sampl ingthe gases a f te r they have passed th e bo i le r tubes and f romthe furn ace; these are designed to reduce the possibi li tyof catalyt ic act ion betw een the points of sampling an danalyses. A t the lower t empera tu res an i ron p ipe wi thg lass lin ing is used, and a t fu rnace tem pera tu res a copperglass-l ined water-cooled samp ler. A s u c t i o n p u m p d rawsthe gases at a constant rate of 0.1 cub ic foo t per minu teth rough the appara tus which absorbs the su l fu r gases ,a f te r wh ich they pass th rough a f lowmeter . The ab -so rp t ion appara tus fo r the S O 3 an d SO2 determinat ion

. . . . . .

H E impor tanc e of th e effect of th e small concentrations

of sulfur dioxide an d sulfur trioxide in boiler-furnace

T ases on th e life of th e refractories, on the externa l cor-rosion of economizers and pre heat ers, and on th e pollution ofthe outside air has m ade it desirable to hav e a small portableappa ratus th at can be used for the rapid determ ination ofthese gases in th e rang e of concentration in which they existin a boiler furnace. The a ppara tus here described is theresult of work carried out by the Pittsburgh ExperimentStation of the U nited Sta tes Bureau of Mines in a n investiga-tion of the service conditions of refractories, conducted jointlywith the Special Research Committee on Boiler-FurnaceRefractories of the A merican Society of Mechanical Engineers.The appar atus was checked for accuracy and mad e up into atest k i t a t the Engineering Experiment Stat ion of the Uni-versi ty of Illinois for use in an investigation of the prevention

of corrosion by flue gases, being conducted in cooperationwith the Utilities Research Commission.

The methods for the determination of SOz and 803 t h a thave been described in the literature ha ve no t proved suitablefor analysis of boiler-furnace gases. Th eir deficiencies ha veexisted in one or more of the following features: (1) Iodo-metric or other reductimetric meth ods are excluded becauseof the existence of reducing agents in the gases besides SO2;

2) the condensation of H2SO4 even a t temp eratu res as high

1 Received April 19, 1929. Presented as a part of the Symposium on

Boiler Room Chemistry before the joint meeting of the Divisions of Indu s-

trial and Engineering Chem istry, Gas and Fuel Chemistry, and Water

Sewage, and Sanitation Chemistry at the 77th Meeting of the American

Chemical Society, Columbus, Ohio, April 29 to May 3, 1929

2 Published by permission of the Director, U. S. Bureau of Mines, and

the Director of the Engineering Experiment Station, University of Illinois.

(Not subject to copyright)

. .

consis ts of one bott le with a fine-grained dry alu nd umthim ble which retain s the droplets of HzSOa nd a secondbo t t l e wi th a coarser a lundum th imble immersed in aNaOH so lu t ion con ta in ing some H20awhich absorbs theS Oz . Water i s run th rough th e g lass tub ing in to t he f i r stth imble and bo t t l e and the SO8 determined by t i t ra t ingwith NaOH.

The second bott le is t i t rated with s tandard acid to de-t e rm i n e t h e SOp.

Results of tes ts to determ ine th e accuracy of th is m ethodare given. When on ly th e to ta l su l fu r is requ i red , thefirs t bot t le is om it te d; if t he gases conta in soot and t arwhich would clog the a lun dum th im ble , the impingerprinciple is u t i l ized, there being two impinger bott les inseries. Th e composit ion of t he gases by Orsat is alsodetermined and f rom these da ta and the coa l ana lys isthe ra t io of t he su l fu r in the gases to th a t in the coa l canbe computed.

. . . . . .

a s 200 C. preve nts the collection of th e gas for subse quen t

analysis; and 3) th e rapid oxidation of SO2 by th e oxygenpresent in th e gas prevents scrubbing the gas by w ater or anysolution before the se pa rat ion of SO2 an d 8 s has been made.A simple portable apparatus that can be assembled in theaverage power-plant lab orato ry is essential.

Hawley ( 2 ) has shown that, although so3 combines withwater vap or to form a fog which will pass through wa ter ora solution of a lkali with out being completely absorbed, it maybe sepa rated from the gases by a filter. Nestell and Anderson3)used Hawley's method for the separation of SO3and SO2

by employing a pape r filter. Th e SO2 was then absorbedan d oxidized by an excess of a stan dar d solution of Na&0 3containing HzOz. The so collected was determined bytitration with standard alkali and the SO2 was determinedfrom th e excess Na2C03 by titration with standar d acid. The

application of these principles ha s led to th e development ofa simple and rugged portable appar atus suitable for power-plant work.

Reactions of Su lfur in Com bust ion of Coal

Sulfur occurs in coal in amounts ranging from 0 5 to 7per cent. When coal is burned on a grate or in powderedform, a certain percentage of sulfur, usually low, remains in

the ash and the remainder u nites with the oxygen and passesout of the furnace with the gases. Sulfur dioxide may beassumed to be the primary produ ct of t he combustion, andth e p resence of 803 is due t o oxidation of SOz at temperatureslower th an those of co mbustion.

The reaction of SO2with oxygen is very slow except in thepresence of c atalys ts. I n boiler furnaces the ash particles

carried by the gases, as well as surfaces with which the gases

calculation of the compounds in portland cement

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