Oct.,
O F IAVDCSTRI.lL
T H E JOI'R.V.1L
IOT?
tions; a n d from 5 t o 3 0 per c e n t , t w o a n d often three.
T o t h e nitric acid solution is n o w added a m n i o n i u m molybdate t o precipitate t h e phosphorus which is determined I>y the p e r m a n gan a t e oxi d R t i o n m e t h o (1 in the usual m a n n e r . If t h e v a n a d i u m h a s n o t been completely separated from t h e phosphorus i t will be indicated b y t h e orange color of t h e a m m o n i u m p h o s p h o in 01 y11 t i a t e precipitate which i s ci u i t e char acteristic; also by t h e tendency of t h e precipitate t o f o r m quickly and adhere t o t h e glass. Results obtained b y this m e t h o d are given in t h e following tnhles: Table I shows t h e results obtained from ;I mixture of s t a n d a r d solutions containing iron, phosphorus a n d vanatliutn in proportions approximately those f o u n d in v a n a d i u m steels. TABLE I Jron taken, I gram; vanadium, 6 . 7 5 my. in first 1 I and 27 mg. in l a s l four T h e actual weight of phosphorus experiments, phosphorus, 2 mg. varied from 1 S Y my. t o 2 . 4 0 mg.. h u t for convenience oi compurisou all were calculated t o a 2 mg. basid.
Milligrams of phosphorus found
TAB1,E
2.01 2 03
I .Y8
2.01
2.13
2.03
I ,9,5
2.00 I ,Yi
II--RIf
STEEL C O N -
0 l i PER CEST \INADIUM .wn 11.03i PER C E N T PHOS-
TAINIX~: PHORlTS
Percentage phosphorus found
(:rams steel taken
KO.
, , ., ., . ,. . . . . . . . . 3.. . . . . . . . . 4 , . .,, ,, . ,
1 ,.. 7 . .
5 h.
.
.
.
.
.
1.2377 m
,
0,0353
n. 8
0.0352 n 0340
2.9114
n. oxso
2..55.18 7 54.11)
,
.
0.034; 0.0756
3 . 9635
T,ABLE I I I - R E ~ C J L TO~S T l v O B~JREAL'O F STANDARD STEELS T O A D D E D ~ A S h D I U MI N \ - A R I E D
i%MOlrNfS FROM
0.5
PER
WHICH WAS
CENT
UP T O 30
PER C E S T O F T H E \VHOI.E WZIGHTTAKEN S1et.l taken ( :r P n 1s
I
I 4102 I5;S'l
0 i
.
1.474Y
I1 5
. .
I ,5297 I iOY0 I 501 i I ,.io?'! I5010 1 0462 I ,0088
I1 . 5
> .3 4..
5 6 I
.
8. Y
10 II
,
,
.. . . 13 . , . . , . ,
12
14
Percentage Percentage \.;inndium phosphorus ncliled in the steel
, , ,
, ,
,
IS.,,,, , . . 16 . , , . . , , 1i , , , . , , 18 ... IY . . . . . . 20 . . 21 . . . . . 2' ,
5
0
05 11 5 1) .i li i
Percentage phosphorus found
0,093
0 096
0 09s 0.0Y.3 0.0Y3 0,043 0 0Y3 0.0Y3
0.092 0.0Yli 0.094 0.101 0.I08 0.097 0 08') 0.I10 0.I 1 3 n III o . in9 0 IOi 0 119 0.113 I1 116 I1 I l l
n
1.1064
1
1.1623 1.0244 1 ,046')
I > 5
0,9995 1.0092 1 ,0055
20 20
093 0 112 1J 1 1 2 0 112 n 112 0.112 n 112 0.112 0.112 I ) . I12
I 0040 I .00ii 1 .00Y5
21)
0.II2
30
0.112
so
0.Il'
0.111 0 . 10) 0 103
I.01Oi
,311 30
U.II?
u
1 00Y2
I I
3
(I
I12
106 (I. I 1 4
Although some of t h e results in the above tables are not a s concordant as might lie desired, yet it is believed t h a t they m a y be t a k e n :is satisfactory for so troublesome a determination. U N I V E R S I T Y OF &IIN.?.ESOT.+
~R.~INKEAPOLIS
A FUSION METHOD FOR THE DETERMINATION OF SULFUR IN IRON AND STEEL D y FREDERICK H. FRANKLIN' Received June 6, 1913
T h e accurate determination of sulfur in iron a n d steel presents m a n y difficulties, owing t o t h e extremely variable a n d complex n a t u r e of t h e iron-carbon alloys. I t has been shown t h a t sulfur combines with manganese in preference t o iron.? Therefore, in most commercial iron a n d steel alloys we h a v e t o deal with t h e former sulfide. I t has been found t h a t t h e insoluble residue left on dissolxTing iron for t h e sulfur determination usually contains some sulfur a n d this must be determined in accurate work. I t is also well k n o w n t h a t when much cementite is present volatile c o m p o u n d s of sulfur and carbon are formed which are difficult t o oxidize a n d so escape estimation. I t m a y readily be seen therefore t h a t t h e m e t h o d employed should he capable of giving a correct measure of t h e t o t a l sulfur n o m a t t e r whether i t exists in one or all of t h e above combinations. F o r t h e purposes of this paper i t will be sufficient t o describe briefly one representative from each of t h e t w o principal classes i n t o which t h e sulfur m e t h o d s m a y be divided. T h e volumetric or evolution m e t h o d is in very general use a n d is usually modified by i t s advocates t o meet t h e existing conditions. T h e gravimetric or oxidation m e t h o d possesses some advantages over t h e former a n d is believed t o be t h e most accurate m e t h o d now in use. Both of these methods have a multitude of modifications a n d t h e mere s t a t e m e n t t h a t sulfur was determined b y t h e volumetric or by t h e gravimetric m e t h o d is n o proof t h a t t b e figures reported are t h e most accurate obtainable by t h e class chosen. .The L'olumetric OY Eaolutiorr Method.--In i t s simplest form this m e t h o d consists of dissolving t h e metal in 1 . 1 sp. gr. hydrochloric acid a n d passing t h e evolved gases through a n a m m o n i a c a l solution of c a d m i u m chloride. T h e mixture of c a d m i u m sulfide a n d dilutcx a m m o n i a is acidified with hydrochloric acid and t i t r a t e d with a solution of iodine t h a t h a s been s t a n d ardized either against sodium thiosulfate or iron of k n o w n sulfur c o n t e n t . T h e chief advantages of this m e t h o d lie in its rapidity a n d t h e index of t h e a m o u n t of sulfur afforded b y t h e precipitated sulfide. F o r most irons a n d steels this m e t h o d when properly carried o u t gives results t h a t agree fairly well with those obtained b y t h e gravimetric method. T o overcome t h e shortcomings of t h e m e t h o d some a u t h o r s propose annealing t h e drillings which b y changing cementite. martensite, e t c . , i n t o pearlite, prevents loss of sulfur as volatile compounds. I t is also c,laimetl b y other writers t h a t by passing t h e evolved gases through a red hot t u b e , the c a r b o n sulfur c o m p o u n d s are broken down t o hydrogen sulfide. A G e r m a n Commission,? appointed by the l'erein Deutscher Eisenhuttenleute t o investigate t h e del Cf. Saunders and Franklin, (lfficial chemist? for the Piew England Foundrymen's Association. 1897, 7 2 . 9 Carnot and Goutal, ComPl. r e n d . . 1897, 125; J . C. S., 3 Schwefelbestimmung in Eisen u. Stahl. Stahl u Eisen. 28 J a h r . , I i r . 8.
T H E J O U R N A L O F I N D U S T N A L AiVD E N G I N E E R I N G C H E M I S T R Y
y40
termination of su!fur in iron a n d steel, considered t h e use of hydrochloric acid of 1.19 sp. gr. absolutely necessary a n d t h a t when used, t h e passage of t h e evolved gases through a red h o t t u b e can be dispensed with. T. Gifford Elliot,’ in t h e .Tour)iul of the I r o i i and Steel Ilzstitutr, combines t h e annealing and strong hydrochloric acid modifications a n d when t i t r a t i n g runs i n a n excess of s t a n d a r d iodine solution :inti t i t r a t e s back with sodium thiosulfate. The Gravimetric or O x i d z t i o u Method: T h i s is usually executed b y dissolving t h e iron or steel i n strong nitric acid. T h e solution is evaporated t o dryness, b a k e d , redissolved in strong hydrochloric acid, diluted, filtered a n d t h e sulfur precipitatecl as barium sulfate. T h i s method is also modified a t several stages,’ t h e most i m p o r t a n t of which are solution i n nitric acid a n d removal of excess acid before precipitation of b a r i u m sulfate. Potassium bromide a n d chlorate are used b y Noyes t o p r e v e n t loss of sulfur during solution a n d t h e same a u t h o r separates t h e iron b y a m m o n i a before precipi t a t i n g t h e b a r i u m sulfate. I n nearly all methods, however, t h e b a r i u m sulfate is formed i n t h e presence of a large a m o u n t of ferric chloride a n d no attention is paid t o t h e iron retained b y t h e b a r i u m sulfate. T h a t t h e oxidation m e t h o d h a s m a n y failings is indicated b y t h e numerous a t t e m p t s t o overcome t h e m b y modifications. T h i s is one of t h e principal reasons t h a t led t o t h e development of t h e new m e t h o d which is called t h e Fusion M e t h o d a n d is t h e result of a search for a method capable of giving a c c u r a t e results with a n y kind of iron. It was desired t h a t solution of t h e iron be effected without t F e use of acids a n d t h a t t h e sulfur be precipitated as b a r i u m sulfate without t h e presence of iron salts. H a v i n g observed t h a t t h e carbonaceous residue obtained b y t h e solution of iron i n copper-potassium chloride solution contained sulfur, a n experiment was carried o u t t o learn how much of t h e t o t a l sulfur i t contained. A few, g r a m s of cupola iron (pig iron remelted in t h e cupola) were dissolved i n a solution of copperpotassium chloride a n d filtered t h r o u g h asbestos. T h e carbonaceous residue was mixed with sodium carbonate, sodium peroxide a n d a little sugar, t h e n ignited b y a h o t wire. T h e aqueous solution of t h e fusion was acidified with hydrochloric acid heated t o boiling a n d t h e sulfur precipitated by b a r i u m chloride. T h e results were surprising, giving a greater percentage of sulfur t h a n was obtained b y t h e volumetric method. A large n u m b e r of experiments were carried o u t a n d all results agreed closely with t h e gravimetric figures. A search t h r o u g h t h e l i t e r a t u r e o n sulfur was made nnd t h e nearest approach t o t h i s m e t h o d was found in a n article b y C. Meineke i n Zeitschrift f u r anger wandte C h e ~ z i e . ~T h e a u t h o r dissolves t h e iron b y boiling with a solution of copper-ammonium chloride, I
“The Volumetric Estirnatiou of Sulfur iu Iron and Steel.” J . I .S. I.,
1911,No. 1. 2
8
Barnber, J 1. S. I., 1, 319 (18Y1) Abstract in Chem. News, March I, 1889
Vol. 5 ,
NO.I O
acidified with hydrochloric acid, a n d t h e n a f t e r filtering off t h e insoluble. dissolves it in a n oxidizing acid and, after evaporating t o d e h y d r a t e silica, filters and precipitates sulfur as b a r i u m sulfate. T H E FUSION METHOD
This method. is given with considerable detail, not because this is necessary for accurate results b u t because of a desire t o assist those who are not familiar with t h e technique of t h e operations involved. ’[‘he sample should be prepared with care a n d should l)e moderately fine; clrillings made slowly with a rather d u l l drill are best. SOLUTIONS,
E’I’C., K V Q U I K E D F O K
T H E FUSION LIETHOD
C o p p e r - Potussium-Burium Chloride SoluLion. -~Dissolve 600 grams of copper-potassium chloride in warm water, a d d 30 cc. of hydrochloric acid, 30 cc. of barium chloride solution, a n d dilute t o 1600 cc. After standing 24 hours, filter t h r o u g h asbestos. S o d i u m Peroxide is practically free from sulfur. Anhydrous S o d i u m Carbonate is free from sulfur. B a r i u m Chloride Solution of 2 0 per cent s t r e n g t h . Hydrochloric , 4 d , C. P., h a s a density of a b o u t 1 . r 9 . Dilute Hydrochloric Acid.-Add I O O cc. of hydrochloric acid t o goo cc. of distilled water. Asbestos Suspension.-The acid-washed fiber is ignited a n d again washed with dilute hydrochloric acid a n d k e p t suspended i n water. Dissolve 3 g r a m s of sample in a b o u t 1 2 0 cc. ol copper-potassium chloride solution containing b a r i u m chloride, b y means of a suitable stirring device. X J u n o motor i n series with a n incandescent l a m p gave excellent service. Allow t h e solution t o s t a n d a b o u t t h i r t y minutes, t h e n d e c a n t upon a n asbestos p a d f o r m e d i n a porcelain Gooch crucible, using suction t o h a s t e n filtration. Wash t h e residue i n t o t h e crucible b y means of a fine s t r e a m of dilute hydrochloric acid, using a s little a s possible. After acid has r u n t h r o u g h , a d d j u s t enough fine asbestos suspension t o cover t h e , carbonaceous residue. Finish washing with 1 5 t o 2 0 cc. of w a r m water. After all h a s passed t h r o u g h , wash down t h e sides of t h e crucible with a few drops of alcohol. Remove t h e p a d a n d residue with tweezers, a n operation easily accomplished if t h e crucible h a s a removable b o t t o m . S e p a r a t e t h e asbestos as completely as possible a n d d r y t h e black residue a t a t e m p e r a t u r e slightly under 100’ C. for a b o u t 1 5 minutes. Weigh 3 g r a m s of a n h y d r o u s sodium c a r b o n a t e a n d mix with it t h e dried residue b y means of a small glass m o r t a r a n d pestle. Transfer t o a nickel crucible of 2 0 cc. capacity a n d incorporate 3 g r a m s of sodium peroxide. Place t h e covered crucible over a small flame a n d h e a t till t h e gentle oxidation is completed a n d t h e melt is quiet a n d homogeneous. T h i s operation requires only a b o u t z or 3 minutes a n d should n o t be continued longer or much nickel will be dissolved. While t h e melt is solidifying, cause it t o cover t h e sides of t h e crucible. Rinse off t h e outside of t h e crucible a n d place in a small beaker containing 5 0 cc. of h o t water and warm until t h e fused mass is de-
T H E JOLrR$.4L O F I Y D U S T R I . 1 L
Oct., 1913
tached. -4fter removing a n d rinsing t h e crucible, a d d 1 5 cc. of hydrochloric acid, using precautions t o prevent loss. After boiling this solution until clear, evaporate t o dryness i n platinum arid heat in oven a t 130'-13j' C. t o d e h y d r a t e silicic acid. Dissolve t h e residue i n jo cc. of distilled water containing I cc. of hydrochloric. acid, filter anti wash until a filtrate of a b o u t 9 0 cc. is obtained. H e a t t o near t h e boiling point a n d a d d 7 c c . of hot 30 per cent b a r i u m chloride solution, drop by d r o p , keeping t h e t e m p e r a t u r e near t h e boiling p o i n t . -4 Schuster dropping flask (shaped like a t i n y r e t o r t ) is c,onvenient for this purpose. Keep t h e beaker with t h e precipitate warm for soin? time a n d allow to s t a n d over night or a b o u t r g hours. Collect t h e barium sulfate o n a n CiSkJeStos pad in d pIatinui11 C;ooch crucible, wash, ignite a n d weigh. W i t h steels a n d low silicon irons t h e m e t h o d m a y be shortened b y omitting t h e evaporation t o remove silica, if t h e a m o u n t of asbestos fused with t h e residue is n o t large. Should a slight precipitate of manganese dioxide appear i t m a y be dissolved b y t h e addition of 3 minute crystal of t a r t a r i c acid, which usually produces a sparkling light green solution. I n t h e following table of results, those obtained by the volumetric: m e t h o d are m a r k e d v , a n d those by t h e gravimetrii:, g.' '1'.4B1.%
LIP KtiSLILTS
Percentages sulfur Percentage Sulfur
Sainglr Bureau of S t a n d a r d s
. . .... . .. .. . . R. . . . . . . . C 2nd . .. . .... C 2nd.. . ....,. . c 2nd. . . . . . . , L) 3 r d . . . . .. . . .
C renewal
.
n... .... n.. . . , . .
D 3rd.. , IJ4 BeS StKel . ... .-\mer. F d y . 4 w i , -\
< u g u l ~ ircrii .
0.035 0.03Y
0.039 0.039 0.034 0 034 0.034 0 os5 11 o i i
0 118
.).
I J . 056 Number 38676 216in ,17485
0.039 0 038 0.044
0.032 p 0.042 g 0,036 li'
0.041 0.032 0.036 0.043
0 036 0 041 I).124
...
...
... ... 0.041 g
0.036 z' 0.115 g
0.057 CJ 1 7 7
0 123
0 . I55 zr 0.113 il 0.105 2'
40101
165 1Y I6450
11 128 I1 124
1641Y .50253 lb51Y 41 1 i . i
IJ. 126
0.107 %' 1) 1 1 5 g
0.0YS
p.092
0.128
0 .I 1 6 8
0.131 0 lit)
(1.096 u 0.l101.
0.054
0 054 g
34345
,39345
(C:u = 0.76$&) 30402 19 765 29949 '9949 278Y 1816Y
White irous Chilled roll., , , , . , , , . . , Malleable, a s cast.. , . , . . Malleable, a s c a s t . , . . , . , Low sulfur steel.. , . . . . . ,
Other methods
0.108 0 102 0.160 0 . 116 0 . 165
1YYY1 1Y34.5
Pig irons
Fusion method
41632 4178U
0.057 j . 0 . 130 $8 0 . 101 s 11 147
~8
0 105
2)
*J
0.053
0 040 I'
0.075 0.047 0.051 u.095
0 074 c: 0.047*J
0 04Y
1J 044 3
0 1;0
0.160 g 0.095 s 0.128 c 0 O!Og
U,14P U . 168
0.014
. . 0 081 g
Numerous blank tests u e r e run, usiug regular amounts of reagents under t h e same conditions as the analyses themselves and the average a m o u n t of sulfur found was 0.0013 per cent.
E X P E K I ME S T A L
I t was t h o u g h t a t first t h a t all t h e sulfur would not Le obtained in t h e carbonaceous residue b u t m y earliest experiments always gave results t h a t agreed well with t h e analyses of t h e Bureau of S t a n d a r d samples. Carnot and Goutall have shown t h a t "When iron or steel is heated with dilute acids, almost all t h e sulfur is converted into hydrogen sulfide b u t when t h e solvent is a neutral or faintly acid solution of copper-potassium chloride all of the sulfur remains in the residue, partly as ferrous sulfide, b u t often mainly as cupric sulfide. Direct, examinatioii shows t h a t the copper solution has no effect. on ferrous sulfide a n d it follows t h a t thy sulfur is partly present in the metal as some other sulfide. I.)irect examination also shows t h a t t h e sulfur in combination with copper in t h e residue is equivalent, t o t h e manganese in t h e iron or steel. Hence p a r t of t h e sulfur is iii combination with manganese as m a n g a n o u s sulfide." Should a n y sulfur pass i n t o solution i t will immediately f o r m barium sulfate with t h e excess of barium chloride present in t h e solvent. hIoreover, t h e solvent is s a t u r a t e d with b a r i u m sulfate so t h a t precipitation is immediate. A few experiments in support of these views a n d some others which show t h e effect of free hydrochloric acid on t h e solubility of barium sulfate are given below: B a r i u m S u l p h a t e i s C a r r i e d Dowlt b y C a r b o i t 1-4 cc. of BaClz solution were added to a I gram sample of shot iron while dissolving in copper-potassium chloride solution. After filtering as usual, z grams of granular zinc were added and the solution rotated rapidly till clear. No precipitate was found in hours. 11-Sample treated as in preceding experiment but z cc. of A7/20 &So4 were added before filtering. Copper was removed b y granular zinc but no precipitate found. 111-To the last test (II), z CC. N,.'zo HzSOI were added and a precipitate formed immediately. B a r i u m Sulfate i s Insoluble i n the Ferrous-Cuprous Solufio,t IV--2 grams of pig iron dissolved in CuKBaCl solution gave 0.096 per cent S or 0.0140gram BaS04. \'-z grams of pig iron dissolved as before and z cc. of N / z o &So4 added, stirred j minutes longer and allowed t'o settle forty-five minutes on oven. BaS04 precipitate could be distinctly seen. The iron contained the equivalent of 0.0140 gram of Bas04 and 0.0116 gram was added giving a total of 0.0256 gram and 0.0245 gram was found. Results but O . O O I gram low, showing practically no loss of BaS04. Barium Sulfute i s Precipitated Immediately u r d Cotnplrtzly 1'1-2 grams of high sulfur iron (S = 0.27 per cent) were dissolved in CuKBaCl solution. Remained on oven one hour and filtered. The filtrate divided into two portions. A-Placed in long Xessler tube and kept on oven z 4 hours. No precipitate visible. After filtering through Gooch, no gain in weight. Absence of BaS04. B-Placed in long Nessler tube and I cc. of H2SU4 v.006 gram of BaS04) added. After standing 011 oven 2 hours, precipitate of Bas04 was distinctly visible. After 24 hours, filtered on Gooch and weighed 0.007 gram. The residur was tinged with iron oxide. 3'0 L e a r n aj Bu.YU, .Srpurutt.s j'rotn l f i g i i .Sulfiir S u m p l r s otl Long .Stunding VII-3 samples uf cast iron, 47006-47007-~7ooX, were carried
' Lou. cit.
THE' J O l y R I V . l L O F I , V D l ' S T R I . - I L
842
through for sulfur, uiing CuKBaCl
solution
and
gavc :
---
Percentages s u l f u r
Vel mrthoil
Fusion method
NO.
0,136 0.121 lost
4iO06
47007 47008
0.114
0.109
n . 106
The filtrates from above stood on the oven for 4 days, then were filtered through paper and carefully washed with dilutc HC1 and water. They weighed as follows: 4 i 0 0 6 . ..
. . . . . . . . . . . . . 0.0014 gram 47007.. . . . . . . . . . . . . . 0,0050 gram 47008.. . . . . . . . . . . . . 0 . 0 0 2 5 gram
These tests deposited basic salts while standing on oven, to dissolve which they were treated twice with z cc. of HCI, but this did not prevent appearance of basic salts. On filtering no indication of BaS04 was noted and only an iron stain remained on paper. The 3 filter papers were ignited and weighed separately, then combined and fused with Na2COs, the solution made faintly acid with HC1 and evaporated to crystals. The residue was dissolved in I O cc. of water and only a slight flocculent precipitate was visible (SO*?). Effect of Hydrochloric Acid on the Solubility of Barium Sulfate 1'111-Four solutions were prepared, each containing 3 grams of sodium carbonate and sodium peroxide, made just acid to methyl orange with HC1. 5 cc. *V/'zo H&Ol were added to each ( =o.ozg4 gram BaS04). HC1 was added in increasing amounts to each test as follows: 2
3
0 . 5 0 cc.
1.00 cc.
1
HCI.. . . . . . . . 0 . 2 5 cc.
4 2 . 0 0 cc
Tests were heated to boiling and slowly precipitated with 7 cc. hot BaCL solution, using a Schuster bottle. Volume = IOO cc. All precipitates were granular and settled rapidly. All precipitates were collected on a carefully prepared asbestos pad and the following results were obtained: 1
G r a m BaSOI. . . . . . . . . . 0.0303 184 WHITTIER AVE. PROVIDENCE, R . I.
2 0.0504
3 0.0290
4 0 . 0 3 12
THE ANALYSIS OF ALLOYS OF LEAD, TIN, ANTIMONY AND COPPER By D. J. DEMOREST
Received June 2, 1913
T h e following m e t h o d of analysis h a s been devised after m a k i n g h u n d r e d s of determinations o n alloys a n d mixtures of metals. T h e earlier results mere i n a c c u r a t e b u t t h e y showed t h e sources of error a n d ways f o r i m p r o v e m e n t i n t h e manipulation until t h e m e t h o d as here presented is, i n t h e writer's opinion, t h e best m e t h o d f o r obtaining quick a n d fairly a c c u r a t e results i n t h e analysis of t h e alloys of t h e a b o v e n a m e d metals. T h e results o b t a i n e d a r e reliable t o within 0 . 2 per cent f o r lead, t i n a n d a n t i m o n y a n d 0.1 per cent for copper. When fine shavings of a n alloy containing a n y or all of t h e metals lead, t i n , a n t i m o n y , a n d copper a r e digested a t a boiling h e a t with concentrated sulfuric acid, t h e lead is left insoluble as PbSO, while t h e tin goes i n t o solution as S n ( S 0 4 ) 2 ,copper as C u S 0 4 . a n d a n t i m o n y as Sb?(S04)3. T h e lead sulfate is filtered off a n d weighed a n d t h e a n t i m o n y i n t h e filtrate is
A-VD E-VGI.VEERI.?JG C H E J I I S l R Y t i t r a t e d with s t a n d a r d cording t o t h e reaction: ,jSb~(SO,)~ 4KLIn0,
+
permanganate
+
T'ol.
j,
SO.I O
solution
nc-
+
24H,O = 10H;jSh04 4hlnSO, 2KyS0, 9H2S0, After t h e a n t i m o n y is t i t r a t e d , t h e t i n is reduced with iron in t h e presence of precipitated a n t i m o n y a n d t h e s t a n n o u s iron is t i t r a t e d b y s t a n d a r d iodine s 01 uti o n . I n a n o t h e r s a m p l e t h e lead is s e p a r a t e d as a b o v c , a n d from t h e filtrate f r o m t h e lead sulfate t h e copper is precipitated as C u C N S either with or w i t h o u t a previous t i t r a t i o n of t h e a n t i m o n y as t h e chemist m a y prefer. T h e C u C N S is t h e n t i t r a t e d with K ? \ l n 0 8 or t h e copper is determined b y t h e very nccwrnte iodide m e t h o d . T h e new t h i n g s a b o u t t h i s m e t h o d are: F i r s ! , t h e t i t r a t i o n of t h e a n t i m o n y b y p e r m a n g a n a t e in n sulfuric acid solution free f r o m H C I ; s e c o i i d , t h r combination of these four m e t h o d s for l e a d , a n t i m o n y . t i n , and copper; a n d third, t h e manipulation necessary for t h e combination. A g r e a t m a n y determinations were m a d e before t h e manipulation necessary t o o b t a i n a c c u r a t e results was worked o u t . I t is necessary t h a t t h e details as here given b e strictly a d h e r e d t o , b u t t h i s is easily done. Procedure.-Place I g r a m of fine shavings or drillings i n a Kjeldahl flask with a s h o r t neck, a n d add 20 cc. of concentrated sulfuric acid. H e a t nearly t o boiling a n d continue t h e h e a t i n g until t h e s a m p l e is nearly decomposed a n d t h e lead sulfate is white. T h i s m a y t a k e one-half h o u r . Finally boil for several minutes. Cool t h e solution a n d t h e n a d d j o cc. of water while t h e solution in t h e flask is k e p t a g i t a t e d . H e a t t h e liquid t o boiling a n d keep boiling for several minutes. T h i s is necessary t o get t h e a n t i m o n y sulfate completely i n t o solution, a s i t crystallizes o u t f r o m a cold c o n c e n t r a t e d sulfuric acid solution. Allow t h e lead sulfate t o settle o u t for a b o u t five minutes or until t h e solution is clear, b u t d o n o t allow t h e t e m p e r a t u r e of t h e liquid t o fall below a b o u t 60' C. T h e liquid a b o v e t h e PbSO4 should become clear quickly. If .it does n o t , i t should b e h e a t e d longer. After t h e liquid h a s become clear, p o u r it t h r o u g h a weighed Gooch crucible with a n asbestos m a t . P o u r t h e solution off a s completely a s possible w i t h o u t allowing more t h a n a v e r y small a m o u n t of t h e PbSO, t o go over i n t o t h e crucible. Now i n t r o d u c e I O cc. more of c o n c e n t r a t e d sulfuric acid i n t o t h e Kjeldahl a n d h e a t t o boiling a n d keep boiling several m i n u t e s , cool, a d d 3 0 cc. of water, h e a t t o boiling for a few minutes, allow t h e solution t o cool t o a b o u t j o " C. a n d p o u r i t a n d t h e precipitate of lead sulfate i n t o t h e Gooch crucible. SVash t h e crucible a n d precipitate six or eight times with distilled water, t a k i n g care t o keep t h e volume of t h e filtrate d o w n t o 12.j-1 j o cc. Ignite t h e PbSOr a t n clull red h e a t , preferably in a muffle furnace, for fifteen niinutcs or more, cool a n d weigh. I t contains 68.3 per cent lead. P o u r t h e filtrate f r o m t h e PbSOl i n t o a 4 j o cc. Erlenmeyer flask. h e a t t o 60"-80" C. a n d t i t r a t e t h e a n t i m o n y with s t a n d a r d p e r m a n g a n a t e of a b o u t
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