Dec., 191;
T H E J O U R N A L O F I N D U S T R I A L A N D E ;V GI 1NE E R I LVG C H E M I S T R Y
replaced b y t w o large t a n k s 20 t o 30 ft. in diameter equipped with t h e thickener mechanism. When a batch of lime and soda liquor has been carried t o equilibrium in one of the cooking tanks t h e contents are allowed t o settle, t h e clear strong liquor is drawn off, a n d t h e sludge is sent t o Thickener A as shown on sketch. On its way there it is mixed with t h e overflow of clear wash water from Thickener B . The underflow from Thickener A , consisting of one part solids t o one part solution, is lifted continuously b y a diaphragm p u m p t o Thickener B , mingling on its way there with t h e wash water from the filter. Underflow from B goes t o filter where it receives a wash of clear water a n d drops into the kiln with a water content of 45 per cent. The overflow from B goes t o A and t h e overflow from A unites with t h e strong liquor from t h e cooking tanks t o form liquor of t h e concentration desired. By proper adjustment of the wash water used, t h e strength of t h e outgoing caustic liquor can be readily maintained a t t h e concentration desired, a n d there is no necessity for storing a n y wash water. B y providing several make-up tanks for t h e final liquor (which is customary practice) a n y slight variation from the concentration required may be corrected b y adding t h e necessary amount of strong or weak liquor. From t h e kiln t h e burnt lime goes t o a cooler, thence t o a storage bin, from which it is drawn as desired and p u t through t h e circuit again. The lime should not contain over one per cent caustic when washed in this manner. T h e thickenipg tanks being of great size allow of sufficient flexibility t o enable t h e kiln t o operate several hours without a n y material being sent into the system from t h e cooking tanks, and vice versa. Hence though t h e cooking is on a n intermittent batch system. t h e washing is continuous a n d supplies t h e kiln with a uniform feed as desired. The entire installation could easily be r u n b y three men per shift a n d t h e total expense of causticizing and lime recovery should not exceed $ 2 . jo per ton of lime used.
c 0 N cL G S I 0 N s I-Prior t o a year ago there was little public knowledge of caustic lime waste being successfully reclaimed, a n d t h e generally known failure ,of a pulp mill in S e w England a n d a n alkali works in t h e West ten years or more ago t o solve t h e problem had created much skepticism. 11-The results of several recovery plants t h a t have been in operation for more t h a n a year show t h a t there are no practical or theoretical reasons preventing t h e general adoption of lime recovery even where t h e tonnage is as low as I O tons per day. 111-The factors t h a t have made for success have been mainly t h e adoption of long r o t a r y kilns a n d filters f o r removing all water possible b y mechanical means before feeding mud t o t h e kiln. IV-A further improvement upon t h e process a s now carried on is t o wash t h e sludge according t o t h e continuous counter-current decantation principle, thereby further reducing costs in t h e causticizing department. 307 PHOENIX BUILDING, BALTXXORS
1059
RAPID VOLUMETRIC PROCEDURES FOR DETERMINING COMBINED ALUMINA AND BASIC ALUMINA OR FREE ACID IN ALUMINUM SALTS By WILFREDW. ScoTr Received June 22. 1915
I n the manufacture of aluminum salts, t h e purity of t h e finished product depends upon the control analyses of t h e liquors after mixing and before evaporation t o crystallization. T h e tests must not only be accurate b u t must be rapidly executed. The following procedures, based on well-known reactions, have been worked out a t t h e Laurel Hill laboratory of t h e General Chemical Company, t o meet these requirements. T h e method for determining basic alumina or free acid in liquors and salts of alumina is the writer's modification of Craig's fluoride process.' The determination of combined alumina depends upon t h e acid reaction of aluminum salts towards phenolphthalein indicator, titration being made in hot solutions as recommended b y Schmatalla.* T h e author is indebted t o hlr. W. S. Allen, Chemist-in-charge, Laurel Hill laboratory for criticism and valuable suggestions t h a t have assisted him in this work. The methods as finally worked out are as follows: D E T E R U I N A T I O X O F B A S I C I T Y O R A C I D I T Y O F ALLTMIh-CM SALTS
T h e procedure is based upon the fact t h a t a n excess of neutral potassium fluoride decomposes aluminum salts in solution, forming two stable compounds which react neutral t o phenolphthalein, while t h e free acid remains unaltered, the following reaction taki.ng place: &(S01)3
+ I Z K F + zH2SOI = zAlF3.3KF
+ 3 K 2 S 0 4+ xH2S01.
The precipitate AlF3.3KF is insoluble in a n excess of t h e potassium fluoride reagent, and is not appreciably attacked b y acids or alkalies. Theoretically about 7 parts b y weight of potassium fluoride are required for one part b y weight of aluminum sulfate, b u t in actual practice it is advisable t o use twice this amount. R E A G E N T S REQuIRED-sta?tdard solutions Of S U I f u r i c acid and potassium hydroxide-Half normal solutions have been found t o be of suitable strength. Sodium hydroxide may be used in place of the potassium hydroxide. Phenolphthalein indicator-Alcoholic solution containing 0.1 per cent of t h e reagent. Potassium juoride-The reagent may be prepared b y dissolving 1000 grams of potassium fluoride in 1 2 0 0 cc. of hot, COS-free water, t h e n neutralizing t h e solution with alkali or hydrofluoric acid as t h e case may require, using j cc. of phenolphthalein indicator. Dilute sulfuric acid may be used in place of hydrofluoric acid, in t h e final adjustment, t o get a neutral product: I cc. of t h e solution in I O cc. of CO2-free water should appear a faint pink. The concentrated mix is filtered, if necessary, a n d t h e n diluted t o 2 0 0 0 cc. with COz-free water. T h e gravity will now be approximately 1 . 3 2 (about 3 j 0 Bk.): I cc. contains 0 . j g. potassium fluoride salt. 1
T.J. I.
Craig, J . SOC.Chem. Znd., SO, 185. Otto Schmatalla. Bey., 38, 4; Chem. X'eus, 9 1 (1905), 2373, 236.
1060
T H E JOURNAL OF INDUSTRIAL A N D ENGINEERING CHEMISTRY METHOD
OF PROCEDURE
SOLIDS-3.4038 grams of t h e finely ground sample or a n equivalent amount in solution (100cc. sample containing 34.038 grams per liter) are t a k e n for analysis. T h e powder is dissolved b y boiling with I O O cc. of distilled water in a 4 in. casserole with clock glass cover. T o t h e hot solution I O cc. of N / z H z S 0 4 are added, and after cooling t o room temperature (zoo C.), 18 t o 20 cc. of t h e potassium fluoride reagent are added a n d '/2 cc. of phenolphthalein indicator. T h e solution is now titrated with N / z K O H , added drop b y drop until a delicate pink color, persisting for one minute, is obtained. This titration shows whether t h e product is basic or acid. B A S I C ALUMINA-This is indicated when t h e alkali back titration is less t h a n t h e amount of acid added. Free Ab03 = (cc. HzS04 - cc. KOH) + 4. FREE A C I E - I n this case the back titration of t h e alkali is greater t h a n the cc. of acid added. Free acid = (cc. K O H - cc. HzS04) x 0 . 7 2 . LIQUORS-In works control of liquors t h e specific gravity is taken: 5 cc. are diluted t o 100 cc. with COSfree water, I O cc. of N / z H2S04 added and t h e solution boiled for about five minutes. After cooling, t h e potassium fluoride reagent is added, together with phenolphthalein a n d t h e titration with t h e standard alkali made a s in case of solids. BASIC MIXES-(CC. H2S04 - cc. KOH) X ( 0 . 0 2 4 j X 0.3473 X roo) +- (5 X sp. gr.) = f r e e A2203. A C I D LIIXES-(CC. K O H - CC. H2S04 X 2.45) f wt. of sample = free HZSO,. N E U T R A L mxEs-The back titration of t h e alkali is t h e same a s t h e volume of t h e acid added. NOTES
C02-free water must always be used in titrations with phenolphthalein indicator. This may be obtained by boiling distilled water to expel Con. If the sample does not dissolve clear, digestion with I O to 15 cc. of standard sulfuric acid is advisable. This may be accomplished by boiling the sample, 1 5 to 2 0 minutes, in an Erlenmeyer flask with reflux condenser. Darkening of the solution during the back titration with the alkali indicates that an insufficient amount of potassium fluoride has been added. If this is the case i t will be necessary to repeat the test with fresh solution and larger amount of potassium fluoride. Ammonium salts, if present, must be expelled by boiling the sample with an excess of standard potassium hydroxide solution and this excess determined. The end point may be readily seen by gas or electric light, as well as by daylight. 3.4038 = factor H&O, to multiplied by 4. 0.72 = factor A1203 to H i% divided by 4. D E T E RMI K A T 1 0 N 0 F C 0 MBI K E D A L U M I N A
Aluminum salts react acid t o phenolphthalein a n d are completely dissociated in hot solutions, a n y acid, combined or free, reacting readily with fixed alkalies forming neutral alkali salts. The end point of t h e reaction is indicated b y the pink color produced b y phenolphthalein with t h e excess of alkali. From t h e
Vol. 7, No.
12
amount of caustic required t h e percentage of combined alumina may be calculated, t h e following reaction taking place: Al,(S04)3
+ 6NaOH
=
+
~ 4 1 ( 0 H ) ~ 3Na2S04.
PROCEDURE
The factor weight, 3.4038 grams, of t h e salt is dissolved in a 4 in. casserole with IOO cc. of distilled water, I cc. of phenolphthalein indicator added a n d t h e sample titrated boiling hot with N / z N a O H , added from a chamber burette, graduated from 50 t o I O O cc. in tenths. If t h e sample contains less t h a n 12.5 per cent A1203 a larger amount of t h e material must be taken if t h e chamber burette, graduated as described, is used. T h e solution is kept boiling during the titration and is constantly stirred. Towards t h e end of the reaction the alkali is added cautiously drop b y drop until a permanent pink color is obtained, viz., a color t h a t persists for a t least a minute with t h e solution boiling. Cc. K a O H required divided b y 4 = p e r cent alumina, A&03; or cc. N / z NaOH X 0.0245 X 0 . 3 4 7 3 X I O O +wt. sample = per ceFzzt A1203. CORRECTION F O R mox-Since iron salts also dissociate and are titrated with aluminum salts by this method a correction has t o be made for t h e ferric and ferrous iron present in the material. T h e t r u e value of combined alumina is obtained b y subtracting the per cent FeO X 0.47 F e 2 0 3 X 0.64.
+
DETER1lIIGATION
A
OF
FERROUS
AND
FERRIC
IROK-
gram sample is dissolved in water and t h e iron oxidized with a few drops of strong potassium permanganate, t h e reagent being added until the solution becomes a permanent pink. The excess permanganate is destroyed by addition of a drop or so of normal oxalic acid solution. Total iron is now determined b y titration of t h e solution with standard stannous chloride. The total iron in t h e sample should be between 0.002 t o 0.05 gram. The solution should contain about 50 cc. of hydrochloric acid, I:I. This is heated t o boiling a n d t h e standard stannous chloride added t o t h e hot solution until t h e yellow color of t h e ferric salt just fades. Cc. of the reagent required multiplied b y t h e factor in terms of Fe203 = Total F e 2 0 3 in the sample. On a separate I O gram sample t h e ferrous iron is determined. This is best accomplished by dissolving t h e salt in a n Erlenmeyer flask b y boiling with I O O cc. of dilute HCl, I:I, in a n atmosphere of C 0 2 t o prevent oxidation. T h e ferric iron is titrated with stannous chloride as in t h e first case. T h e difference between the first titration results in terms of Fe20s and t h e second in terms of FesOa percentages is due t o ferrous iron in terms of Fe203. This result multiplied by 0.9 = FeO. T h e accuracy o f t h e titration depends upon t h e absence of oxidizing agents, other t h a n iron, which react with stannous chloride. The reagent should be carefully standardized against ferric ammonium alum. If I 7 . 2 grams of this salt are dissolved in 2 0 0 0 cc., one CC. will contain approximately 0.001 g. of iron. Titration of t h e sample should be conducted under j
Dec.. 1915
T H E J O U R N A L OF 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
conditions of temperature, acid concentration, etc., similar t o those of t h e standardization. T h e a m o u n t of phenolphthalein used should be t h e same i n each determination. An excess of t h e indicator causes low results. It has been noted i n cases of alums, where iron does not interfere, t h a t best results are obtained with three or four drops of phenolphthalein solution. Larger amounts of indicator are necessary if iron is present, in order t o detect t h e end point. C O M B I X E D S U L F U R I C ACID-Provided no free acid is present, t h e combined acid is calculated from t h e titration for combined alumina. T h e titration multiplied b y 0 . 7 2 = c o m b i x e d sulfuric a c i d , ziz., factor 2.8792 divided b y 4. Should free acid be present, as determined b y t h e first procedure outlined, its equivalent should be deducted from both t h e alumina a n d combined acid. This is best done b y subtracting t h e equivalent volume in t e r m s of N / z solution from t h e t o t a l volume titration before dividing b y 4 t o obtain percentage of A1203 or multiplying b y 0 . 7 2 t o get combined H2SOs. EXAMPLE-Titration of N/2 alkali due t o free acid = 2 . 2 cc. (1st method). Total titration of t h e hot solution (2nd method) = 80.6 cc. N a O H . T h e 80.6 - 2 . 2 = 78.4 a n d 78.4 divided b y 4 = 19.6 per cent A1203or 78.4 multiplied b y 0 . 7 2 = 56.45 per cent combined H 2 S 0 4 . Free acid = 2 . 2 divided b y 4 = 0 . 5 j per cent H2S0,. Sulfuric acid combined with t h e fixed alkalies is not t i t r a t e d . E X P E R I 11E N T A L D A T A I N F L U E N C E OF IRON-Iron is invariably present in aluminum salts in ferric or ferrous form, generally a combination of t h e two. T h e a m o u n t seldom exceeds 0.8 per cent F e so t h a t comparatively large a m o u n t s of iron need not be considered here. Since t h e combined acid of iron in either s t a t e of oxidation titrates readily, this impurity will cause a n appreciable error unless allowance be made for t h e a m o u n t present. T h e following results were obtained on a mixture of pure potash a l u m with varying a m o u n t s of iron as indicated, this i m p u r i t y being added as ferric a n d ferrous sulfate. T h e q u a n t i t y of a l u m t a k e n was suffi cient t o give a titration of over 69 cc. of s t a n d a r d alkali. T h e factors 0.64 for ferric a n d 0.47 for ferrous iron t o a l u m i n a were used a s recommended in t h e method. Added iron 0
0 . 1 5 Fe:Os 0 . 5 Yc FezOs 1 , O g FenOa O,lyoFeO 0 . 5 ~ FeO o 1 . O % FeO
Titration l / d Titration Titration 6 9 . 4 ~ ~ . 17.35 Corrected for iron 6 9 . 8 cc. 17.45 17.39 70.85 cc. 17.72 17.41 7 2 . 5 cc. 18.12 17.48 6 9 . 6 cc. 17.40 17.35 70.65 cc. 17.66 17.43 7 1 . 5 cc. 17.88 17.41 I~
I t is evident t h a t with t h e titration representing per cent, iron present either as ferric sulfate or ferrous sulfate u p t o one per cent in t e r m s of iron oxide causes no serious error, provided t h e corrections a r e applied for t h e titration of t h e iron. Ferric iron tends t o cause high results. T h e fact t h a t ferric a n d ferrous sulfates are t i t r a t e d is shown b y t h e results given below. Ammonium
1061
sulfate a n d persulfate are also t i t r a t e d , t h e fixed alkalies are not. Results are given i n terms of t h e acid calculated from t h e titration. Salt used AIz(S01)3.
Gram acid present . . . . . . . . . . . . . . . 0.300 F e S O ~ , 7 H z 0.. . . . . . . . . . . . 0 . 6 9 9 Fez(S0a)a. , , . , , , , , . , , . , . , 0.483 (NH1)2S04.,, , , , . . , . , , , 0 . 742 ( S H i ) & O s . , . . . . . . . . . . . .0 . 8 6 0
Gram acid calculated 0.299 0.636 0.612 0.658 0.850
..
Ammonia is expelled i n t h e boiling solution a s t h e alkali replaces it in combination. Ferrous hydroxide occludes phenolphthalein i n dicator t o a point of saturation. F o r example, i t was found t h a t one g r a m ferrous sulfate w:th excess N a O H would completely absorb 2 5 cc. of t h e indicator preventing i t from giving t h e desired color with caustic, whereas a n excess of t h e indicator above t h i s a m o u n t produced t h e pink color with t h e excess caustic. T h e following results were obtained with three s t a n d a r d aluminum salts b y t h e usual gravimetric methods, a n d t h e results checked b y t h e volumetric procedures outlined: G R A V I M E T RANALYSIS IC Per cent VOLUMETRIC Per cent ALUMINUM SULFATE Combined AlzO3. . . . . . . . . . 17.20 17. 95 A1203 Fezox.. . . . . . . . . . . 0.55 Free A l z O ~ ,.. . . . . . . . . . . . . 0 . 3 6 Fez03 .................... Correction for ferric and A1203 hv difference,. . . . . . . 17.40 ferrous i r o n . , . . . . . . . . . . 0.25 Total AiLh corrected . . . . . . 17.31 RECRYSTALLIZED POTASH A L U M T o t a l AlzOs.. . . . . . . . . . . . . . 10.77 Combined AlzOs.. . . . . . . . . 1 0 . 6 8 Iron.,. . . . . . . . . . . . . . . . . . .Trace Free A1203.. . . . . . . . .. . . . . 0 . 0 4 Total A1zOa.. . . . . . . . . . . . . 10.72 ALVMINUM CHLORIDE Combined AlzOs.. . . . . . . . . 20.45 Total Ala08 FezOz., . . . . . 20.97 Free AlzOs.. . . . . . . . . . . . . 0 . 3 3 FezOs.. . . . . . . . . . . . . . . . . . . 0.023 A1203 by difference.. . . . . . . 20.947 Total.. . . . . . . . . . . . . .. . . . . 20.78 Corrected for iron.. . . . . . . . 20.765
+
+
T h e e n d point is s h a r p when iron is absent, b u t with a m o u n t s of iron exceeding I per cent t h e color of t h e precipitated iron hydroxide t e n d s t o mask t h e pink color due t o t h e indicator. Ferric iron produces a reddish pink end point; with ferrous iron a purplish pink color is observed. Four men working independently checked within 0.6 cc. in t h e titration for combined alumina, a n d within 0.1 cc. in t h e fluoride method for free alumina, making t h e limits of error due t o t h e personal factor, 0.1j per cent for t o t a l A l 2 o 3 a n d 0 . 0 2 per cent for free A1203. A. . . . . . . . . . . . . . . . . . 69.3 B. . . . . . . . . . . . . . . . . . . 3.8
69.4 3.7
69.8 3.8
6 9 . 2 ~ ~ . 3 . 8 cc.
S U 1X MA R Y
R a p i d volumetric procedures for determining combined a n d free alumina in aluminum salts, followed b y experimental d a t a showing reliability of t h e methods, a r e given. Impurities such as commonly occur in these salts do not interfere, with exception of iron, for which correction must be applied a s s t a t e d . T h e methods are of special value for works control of liquors during t h e process of manufacture of aluminum salts, a n d t h e analysis of t h e finished product in daily routine analysis. RESEARCH DEPARTMEW,G E N E R A LCHEMICALC O M P A N Y LAURELHILL, LONGISLAXD,S . Y.
RECOVERY OF AMMONIA FROM WASTE LIQUORS By E. I,. KSOEDLER Received May 22, 1915
A recent investigation of waste products in t h e plant of t h e Welsbach Company brought t o light a
