By G. E. F. Lundell and J. I. Hoffman
B u r e a u o r S t a n d a r d s , D e p a r t m e n t o p C o m m e r c e , W a s h i n g t o n , D . C .
U n fo rtu n ately th ere is available for th e d eterm in a
tio n of cobalt in steels no such simple, rap id , an d ac
cu rate m ethod as th e dim ethylglyoxim e m ethod for nickel. T here are some m ethods, such as th e a - nitroso-/3-naphthol m eth o d 1'* and th e sodium cobalti- n itrite m ethod,2 which aim a t th e sep aratio n of cobalt as such. These m ethods all call for m ore or less in volved prelim inary tre a tm e n ts, an d th e final cobalt precipitates can n o t be directly dried, ignited, and weighed, b u t m ust be converted in to o th er forms.
M ost m ethods for th e determ in atio n of cobalt aim a t th e sim ultaneous d eterm in atio n of nickel an d cobalt w ith subsequent deduction of nickel as determ ined separately. Such are th e p h o sp h ate,3 th e cyanide,4 an d th e electrolytic5 m ethods.
T he m ethod to be described is of th e last-n am ed ty p e and is based, for th e m ost p a rt, on well-known facts.
T h e effects of some interfering elem ents, n o tab ly v an ad iu m in th e electrodeposition of cobalt, have been discovered and overcome. T he m ethod is n o t a sh o rt one and is therefore n o t suitable for ro u tin e works analysis. I t is, however, a w ell-tested, accu rate m ethod which is suited to th e p rim ary stan d ard izatio n of cobalt steels for cobalt an d nickel. In addition, it possesses th e m erit, from th e sta n d p o in t of th e a n aly st engaged only occasionally in th e analysis of this ty p e of m aterial, of providing for th e sim ultaneous accu rate d eterm in a
tion of chrom ium , v anadium , copper, an d m anganese in th e sam e sam ple.
T h e m ethod was developed during th e analysis a t th e B ureau of S tan d ard s of th e R idsdale B ritish S ta n d a rd C hrom e-T ungsten-V anadium -C obalt Steel
“ W .” This steel also contains nickel, m olybdenum , and copper, in ad d itio n to th e o rdinary steel c o n stitu ents. T h e m ethod was also carefully tested in th e analysis of th e B ureau of S tan d ard s C hrom e-V anadium S tan d ard Steel No. 30a, to which h ad been added know n am ounts of nickel an d cobalt.
P R E L IM IN A R Y R E M A R K S O N P R O C E D U R E
T he following digest of th e m ethod will m ake clear th e purpose of th e various steps. T he steel is dissolved in hydrochloric an d nitric acids, and any tu n g stic and silicic acids are filtered off and tre a te d w ith sodium hydroxide. Any insoluble m a tte r is filtered off, dissolved in hydrochloric acid, an d added to th e m ain solution. T he m ajor p a rt of th e tu n g sten an d silicon is th u s elim inated, and an y co n tam in atin g cobalt, nickel, or chrom ium recovered. T he solution is th e n subjected to an eth er tre a tm e n t, which rem oves th e m ajor p a rt of th e iron, to g eth er w ith th e m ost of an y m olybdenum present. T he acid e x tra c t is th en heated w ith Sulfuric acid till fum es escape, afte r which chrom ium , vanadium , and m anganese are oxidized by potassium persulfate. The h o t oxidized solution is poured in to h o t sodium hydroxide solution, and
1 Received F ebru ary 11, 1921.
1 Published b y perm ission of th e D irecto r of th e B ureau of S tand ard s.
* N um bers refer to references a t en d of a rtic le , p. 543.
filtered. T his q u a n tita tiv e ly sep arates chrom ium , vanadium , and any residual tu n g ste n and m olybdenum from cobalt, nickel, m anganese, copper, and iron.
T he p recip itate is dissolved in sulfuric acid by th e aid of sodium bisulfite and tre a te d w ith hydrogen sulfide to rem ove copper q u a n tita tiv e ly . A fter expulsion of hydrogen sulfide and reoxidation, a double p recip ita
tion w ith am m onium hydroxide serves to rem ove iron.
The com bined filtrates are th e n electrolyzed for nickel and cobalt, which are weighed, dissolved, and tre a te d w ith dim ethylglyoxim e to ob tain nickel. M anganese, which does n o t interfere in th e electrolysis, m ay appear as a deposit on th e anode, as a sludge, or rem ain in solution.
P R O C E D U R E
Dissolve 2 to 4 g. of th e sam ple in 50 cc. of dilute hydrochloric acid (1 : 1) and oxidize w ith 5 cc. of co n centrated nitric acid (sp. gr. 1.42). D igest until the tu n g stic acid is b rig h t yellow, ad d 150 cc. of hot w ater, an d boil for 1 min. F ilter and wash free from iron w ith dilute hydrochloric acid (1 : 9). T re a t th e im pure tu n g stic acid w ith a sm all am o u n t of a 10 per cent solution of sodium hydroxide, and if any dark-colored residue rem ains, dissolve it in h y d ro chloric acid an d ad d th e solution to th e m ain filtrate.
E v a p o ra te th is filtrate tw ice w ith 30 cc. of h y d ro chloric acid (sp. gr. 1.2), b u t n o t to com plete dryness on account of th e slight v o latility of d iv an ad y l chloride.
T ake up in hydrochloric acid (sp. gr. 1.11), filter, if tungstic or silicic acid is present, an d sep arate by m eans of e th e r6 th e m ajor portion of th e iron, to g eth er w ith m olybdenum , from nickel, cobalt, copper, chrom ium , vanadium , and m anganese.
Boil th e acid e x tra c t to expel th e eth er, add 4 cc.
of sulfuric acid (sp. gr. 1.84), and ev ap o rate to th e a p pearance of fum es. D ilute th e solution to 300 cc., add 40 cc. of a sa tu ra te d solution of potassium p er
sulfate, an d boil u n til th e m anganese is com pletely precip itated as oxide. T his requires ab o u t 10 min.
P our th e h o t solution in to 200 cc. of a w arm 5 per cent solution of sodium hydroxide. If th e precipitate is not black add a sm all am o u n t of potassium persulfate solution. W hen th e p recip itate has settled , filter th rough asbestos and w ash7 w ith a 2 per cen t solution of sodium hydroxide.8 Place th e crucible w ith th e p recip itate in th e original beaker, add 100 cc. of w ater, 5 cc. of sulfuric acid, and a crystal of sodium bisulfite, and w arm un til th e p recip itate has dissolved. Filter, wash w ith h o t w ater, and rep eat th e persulfate oxida
tion, th e sodium hydroxide p recip itatio n , and th e filtration an d washing, in order to rem ove all chrom ium and vanadium . Com bine th e sodium hydroxide fil
tra te s .9
Dissolve th e p recip itate containing nickel, cobalt, copper, m anganese, and iron as before, filter off the asbestos, neutralize w ith am m onia, acidify w ith sul
furic acid (1 cc. of acid for 100 cc. of solution), and pass in hydrogen sulfide. F ilter off any copper sulfide
June, 1921 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 541 and wash w ith a 1 per cent solution of sulfuric acid
saturated w ith hydrogen sulfide.10
Boil th e solution to rem ove hydrogen sulfide, adding persulfate to w ard th e end to destroy sulfur. Dissolve any m anganese dioxide which has sep arated o u t by the addition of th e least possible am o u n t of sodium bisulfite. M ake am m oniacal and filter.
As th e ferric hydroxide in v ariab ly contains a little cobalt, it should be dissolved in 20 cc. of sulfuric acid (1 : 4), rep recip itated w ith am m onia, an d filtered.11
E v ap o rate th e com bined filtrates to a volum e of 100 cc. In case a p recip itate has form ed, acidify the solution w ith sulfuric acid, add a cry stal of sodium bisulfite, and w arm .
The solution should now contain am m onium sulfate equivalent to 10 cc. of co n cen trated sulfuric acid.
N eutralize w ith am m onium hydroxide (sp. gr. 0.90), and add 35 cc. in excess and 2 g. of sodium bisulfite.
E lectrolyze in a volum e of 150 cc. for 6 to 8 hrs., using gauze electrodes and a c u rren t density of 0.2 to 0.3 am pere per d m 2. W ash th e cathode w ith cold water, d ry a t 100° C., and w eigh.12
The electrolyte, which usually contains from 0.1 to 1.0 mg. of nickel an d cobalt (m ainly cobalt), should be tested as follows: Boil w ith an excess of am m onium persulfate, keeping th e solution strongly am m oniacal to precipitate m anganese, filter, w ash,13 an d tre a t w ith hydrogen sulfide. If a p recip itate form s, filter on a small filter, wash w ith w ater containing a little am monium chloride an d am m onium sulfide, ignite, and weigh as com bined oxides of nickel an d cobalt. M ul
tiply by th e em pirical factor 0.75, an d add to th e cathode w eight.14
Dissolve th e nickel and cobalt on th e cathode an d the oxides recovered from th e electrolyte in 20 cc. of nitric acid (sp. gr. 1.42), neutralize w ith am m onium hydroxide, an d th e n m ake ju st acid w ith hydrochloric acid. A dd sufficient 1 per cent alcoholic solution of dim ethylglyoxim e to re act w ith b o th nickel and co
balt, m ake fain tly am m oniacal, and allow to digest for 2 h rs.15
Filter th ro u g h asbestos, dissolve back into th e orig
inal beaker b y m eans of 20 cc. of w arm nitric acid (1 : 1), and p recip itate and digest as before. F ilter through a ta re d Gooch crucible, wash w ith a little h o t water, dry a t 120° C., an d weigh.
Calculate nickel and subtract from the total nickel and cobalt.
D E T E R M IN A T IO N O F C H R O M IU M A N D V A N A D IU M
If d eterm inations of chrom ium and v anadium are desired, th e tw o filtrates from th e sodium hydroxide separation7 should be com bined and analyzed accord
ing to th e electrom etric titra tio n m ethod of Kelley, Wiley, Bohn and W rig h t,10 Jo h n so n ’s m eth o d ,17 or th e Bureau of S tan d ard s p rocedure,18 which is as follows:
E v ap o rate th e solution, m ake up to exactly 500 cc. and divide in to tw o 250-cc. portions, A and B.
d e t e r m i n a t i o n o f c h r o m i u m— Acidify P ortion A with sulfuric acid, ad d 5 cc. ,of silver n itra te solution (2.5 g. per lite r), an d boil w ith 5 cc. of a 10 per cent solu
tion of am m onium persulfate u n til th e persulfate is
entirely destroyed (ab o u t 10 m in.). Cool, ad d ferrous sulfate, an d titr a te w ith p erm anganate.
In th is operation q u in q u iv alen t v an ad iu m is reduced to th e q u ad riv alen t condition b y th e excess for ferrous sulfate added and th e n oxidized back to th e q u in q u iv a
le n t condition by th e perm an g an ate, th ereb y causing no n et change. Sexivalent chrom ium is p erm an en tly reduced to th e triv a le n t condition. T he chrom ium m ay therefore be calculated from th e difference b e tw een th e volum e of ferrous sulfate add ed and th e ferrous sulfate equivalent of th e p erm an g an ate con
sum ed.
d e t e r m i n a t i o n o f v a n a d i u m— Acidify P o rtio n B w ith sulfuric acid, boil, and reduce in a Jones red u cto r containing ferric alum an d phosphoric acid in th e re ceiver.19 T itra te th e h o t solution w ith perm an g an ate.
In order to o b ta in accu rate resu lts a b lan k (which usually requires a b o u t 0.8 cc. of 0.03 N perm anganate) m ust be carried th ro u g h th e various steps of th e de
te rm in a tio n w ith th e p ro p o rtio n ate am o u n ts of sodium hydroxide, potassium persulfate, sodium bisulfite, and asbestos. In th is o peration v an ad iu m is reduced to th e biv alen t condition and afterw ards oxidized to th e q u in q u iv alen t sta te , while chrom ium is reduced to th e b ivalent condition and afterw ards oxidized to th e t r i v alen t sta te . T he volum e of p erm an g an ate consum ed by v an ad iu m is therefore represented by th e difference betw een th e volum e of p erm an g an ate used in B and o n e-th ird of th e p erm an g an ate equ iv alen t of th e fer
rous sulfate required by th e chrom ate in A.
d e t e r m i n a t i o n o f m a n g a n e s e— M anganese m ay
be conveniently determ ined in th e n itric acid solution (References 11, 12, an d 13), by th e b ism u th ate m ethod.
d e t e r m i n a t i o n o f c o p p e r— C opper m ay be de
term ined as described in Reference 10.
T E S T S O F T H E P R O C E D U R E
T he experim ents listed in T able I were perform ed in order to establish th e accuracy of th e electrolytic m ethod for cobalt and nickel u nder such v ary in g con
ditions as m ight o b tain in steel analysis. Unless otherw ise specified, th e electrolyses were carried o u t in 150-cc. solution, containing 25 g. am m onium sulfate a n d 35 cc. am m onium hydroxide (sp. gr. 0.90), a t 0.20 to 0.30 am pere per d m 2, for 16 hrs.
T he d a ta show th a t:
1—The deposition of cobalt is seldom complete and recoveries must be carried out as specified in the method.
2—The addition of ammonium acetate or sodium bisulfite (particularly the latter) has a beneficial effect.
3—Potassium, manganese, and chromium sulfates, moderate amounts of platinum, and chlorides are without harmful effect.
4— Vanadium does not interfere seriously in the deposition of either nickel or cobalt alone, but does interfere most seriously when both are electrolyzed simultaneously.
5— Tungsten interferes in depositions involving cobalt or cobalt and nickel, but not nickel alone.
6—Ferrous salts, chromâtes, tartrates, and molybdenum interfere markedly.
T able I I sum m arizes th e results obtained in th e analysis, by th e m ethod as described, of th e B ritish S ta n d a rd “ W ” and th e B ureau of S ta n d ard s S ta n d a rd
542 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 Vol. 13, No. 6
Ta ble I — Effec t o p Va r io u s Substances on t h e El ect ro d epo sit io n op Cobalt and Nic k el
W eig h t of W eight of
N ick el-C o b alt D ep o sit on N a tu re
T a k e n C ath o d e of E rro r
Ex p t. S u b stan ces Added G ram G ram D eposits G ram
l i ... 0.0 9 7 7 C o 0 .0 9 6 5 D a rk g ray — 0.0012*
2 i ... 0 .0 9 7 9 N i 0 .0 9 7 0 P la tin u m -lik e — 0.0009*
31 ... 0 .0 9 7 9 N i 0.0977 Co 0 .1 9 3 9 G ra y — 0.0017*
4* 2 g. N a H S O j... 0 .0 9 7 9 N i 0 .0 9 7 7 Co 0.1951 G ood g ra y — 0.0005*
5« 2 g. N a H S O j... 0 .0 9 7 9 N i 0 .0 9 7 7 Co 0.1 9 5 4 G ood g ra y — 0.0002*
6 ... 0.0 9 7 7 Co 0 .0 9 7 2 D a rk g rav — 0.0005*
7 ... 0 .0 9 7 9 N i 0 .0 9 8 0 P latin u m -lik e + 0 .0 0 0 1 * 8 1 g. N H «C tH jO j... 0.0 9 7 9 N i 0.0 9 7 7 Co 0 .1 9 5 2 G ra y — 0.0 0 0 4 9 2 g. N a H S O j... 0.0 9 7 9 N i 0.0 9 7 7 Co 0 .1 9 5 2 G ood g ray — 0.0004 10 3 g. T a rta ric a c i d ... 0 .0 9 7 9 N i 0.0 9 7 7 C o 0 .0 3 0 8 P u rp lish a n d discolored — 0.1648 11 1 g. K jS O i... 0 .0 9 7 9 N i 0.0 9 7 7 C o 0.1 9 4 7 G ood g ray — 0.0 0 0 9 12 0 .0 0 3 5 g. M n as K M n O i... 0 .0 9 7 9 N i 0.0 9 7 7 C o 0 .1 9 4 8 G ood g ra y —0 .0 0 0 6 13 0 .0 0 3 5 g. M n as K M n O i... 0.0 9 7 9 N i 0.0 9 7 7 Co 0.1 9 5 3 G ood g ra y — 0.0 0 0 3 14 0 .0 0 3 5 M n as K M nO i, 1 g. NH«CiHjOi... 0 .0 9 7 9 N i 0.0 9 7 7 Co 0 .1 9 5 3 Good g ra y — 0.0 0 0 3 15 0 .0 1 g. M n as K M n O i, 2 g. N a H S O j... 0 .0 9 7 9 N i 0.0 9 7 7 C o 0 .1 9 5 8 Good g ray + 0 .0 0 0 2 16* 0.0 1 g. M n as KMnO«, 2 g. N a H S O j... 0 .0 9 7 9 N i 0.0 9 7 7 C o 0 .1 9 5 8 Good g ra y + 0 .0 0 0 2 17« 0 .0 1 g. M n as KM nO*, 2 g. N a H S O j... 0 .0 9 7 9 N i 0.0 9 7 7 C o 0.1 9 5 7 Good g ra y + 0 .0 0 0 1 18 0 .0 0 5 g. V as V jO j... 0 .0 9 7 9 N i 0.0 9 7 7 C o 0 .0 2 2 5 ... — 0.1731 19 0 .0 0 1 g. V as VjOi... 0 .0 9 7 9 N i 0.0 9 7 7 C o 0 .1 1 8 5 G ood g ra y — 0.0771 20 0.001 g. V as VaO»... 0.0 9 7 9 N i 0 .0 9 8 3 Good g ra y + 0 .0 0 0 4 21 0.0 0 1 g. V as ViO*... 0.0 9 7 7 Co 0.0971 D a rk b u t good —0.0 0 0 6 22 0.0 0 1 g. V as VjO«... 0 .0 9 7 9 N i 0 .0 9 7 7 Co 0 .1 2 1 2 ... — 0 .0 7 4 4 23 0.0 0 1 g. V as VaO«... 0.0 9 7 9 N i 0 .0 9 7 6 P la tin u m -lik e — 0.0003 24 0 .0 0 1 g. V as ViO«... 0.0977 Co 0.0 9 8 4 D a rk b u t good + 0 .0 0 0 7 25 0 .0 0 5 g. V as VaO«... 0 .0 9 7 9 N i 0.0 9 7 7 Co 0 .0 1 0 0 ... — 0.1 8 5 6 26 0 .0 0 5 gj C r as K tC n O ?... 0.0 9 7 9 N i 0.0 9 7 7 Co 0 .0 0 0 0 ... — 0.1 9 5 6 27 0 .0 0 1 g. C r as K iC rjO r... 0 .0 9 7 9 N i 0.0 9 7 7 Co 0 .0 9 2 2 ... —0 .1 0 3 4 28 0 .0 1 g. C r as Cra(SO«)a, 3 g. ta rta ric a c id ... 0 .0 9 7 9 N i 0.0 9 7 7 Co 0 .0 2 8 4 P u rp lish a n d discolored — 0.1 6 7 2 29 0.0 0 1 g. C r as Cra(SO«)j, 2 g. N a H S O j... 0 .0 9 7 9 N i 0.0 9 7 7 C o 0 .1 9 5 6 G ood gray 0.0 0 0 0 30 0 .0 0 5 g. W as NaaW O«... 0 .0 9 7 9 N i 0.0 9 7 7 C o 0.2011 Good gray + 0 .0 0 5 5 31 0 .0 0 5 g. W as N atW O «... 0 .0 9 7 9 N i 0.0 9 8 3 Good g ra y — 0.0 0 0 4 32 0 .0 0 5 g. W as N a aW O « ... 0.0 9 7 7 Co 0.1 0 3 4 D a rk b u t good + 0 .0 0 4 7 33 0 .0 0 5 g. M o as <NH«)aMoO«... 0 .0 9 7 9 N i 0 .0 9 7 7 C o 0 .0 0 3 2 S lightly co p p er colored — 0.1 9 2 4 34 0.0 0 1 g. P t as Pt(SO«)a, 2 g. N a H S O j... 0.0 9 9 7 N i 0.0 9 7 7 Co 0.1954 Good g ray —0 .0 0 0 2 35 0.0 0 1 g. F e as M o h r’s salt, 2 g. N a H S O j... 0 .0 9 7 9 N i 0.0 9 7 7 Co 0.1 9 6 7 Slig h tly discolored + 0 .0 0 1 1 36 l c c . conc. HC1... 0 .0 9 7 9 N i 0.0 9 7 7 C o 0.1951 Good g ra y — 0 .0 0 0 5 1 E lectrolyzed for 4 hrs. * R ecoveries in th e electrolytes of E x p ts. 1-7 were 0.0011, 0.0010, 0.0015, 0.0001, 0.0000, 0.0006, a n d 0.0000 g., respectively.
* E lectrolyzed for 6 hrs. 4 Electrolyzed for 8 hrs. 4 Solution contained only 13 g. (NH«)aSO«. 8 S olution contained 38 g. (NH«)aSO«.
Ta b l e I I — An alyses Made bvt h e Proposed Method (R esu lts Expressed in P e r cent)
C o b alt N ickel C hrom ium V an ad iu m M anganese C opper
M ate rial Used P rese n t F o u n d P rese n t F o u n d P rese n t F o u n d P re s e n t F o u n d P rese n t F o u n d P rese n t F ound 1 B ritish S ta n d a rd “ W” 1... 4 .7 3 4 .7 8 0 .4 4 0.4 1 . . . . ... 0 .1 0 2 0 .0 9 7 ...
2 B ritish S ta n d a rd " W " » ... 4 .7 3 4 .6 9 0 .4 4 0 .4 2 . . . . ... 0 .1 0 2 0 .1 0 3 ...
3 B ritish S ta n d a rd " W ” ... 4 .7 3 4 .6 9 0 .4 4 0 .4 3 3 .0 3 2 .9 4 0 .7 9 8 0 .7 8 8 0 .1 0 2 0 .0 9 0 0 .0 5 5 0.0 6 5 4 B ritish S ta n d a rd " W ’*... 4 .7 3 4 .6 8 0 .4 4 0 .4 3 3 .0 3 2 .9 4 0 .7 9 8 0 .7 9 5 0 .1 0 2 0 .0 8 9 0 .0 5 5 0.068
2.93* 0.797*
5 B ureau of S ta n d a rd s C r-V S ta n d a rd N o. 3 0 a . . . 2 .4 4 2 .4 5 2 .5 7 2 .5 8 1 .0 2 1 .0 5 0 .2 1 0 .1 9 0 .8 0 5 0 .8 1 9 0 .0 6 3 0 .0 6 2 6 B ureau of S ta n d a rd s Cr-V S ta n d a rd N o. 3 0 a . . . 2 .4 4 2 .4 5 2 .5 7 2 .5 4 1 .0 2 1 .0 4 0 .2 1 0 .2 0 0 .8 0 5 0 .8 2 0 0 .0 6 3 0.068 7 B u reau of S ta n d a rd s Cr-V S ta n d a rd N o. 3 0 a . . . 2 .4 4 2 .4 6 2 .5 7 2 .5 6 1 .0 2 1.0 4 0 .2 1 0 .2 0 0 .8 0 5 0 .8 1 8 0 .0 6 3 0.060
1 W et peroxidation used as describedin R eference 8 . * B y electrom etric titra tio n , K elley, W iley, B ohn a n d W rig h t's m eth o d .
No. 30a to which cobalt and nickel had been added. 3— The determination of manganese is free from the Standard “ W” contains 16.20 per cent tungsten, troublesome interference of chromium or cobalt.
0.05 per cent molybdenum, in addition to the per- 4— Elements like cerium, zirconium, and titanium centages of other elements listed in Table II. The (see N ote 5 below) "would be quantitatively present in values given in Table II are the averages of the ranges the ammonium hydroxide precipitate along with iron, of the values reported by British, Scotch, French, 5— Titanium, if present, would be oxidized by per- Italian, and American chemists, which are as follows: sulfate and might escape complete precipitation by
Cobalt, 4.53 to 5.06 sodium hydroxide. This would affect only the de-a^omiumV9i°t^ 3 l’ termination of chromium and vanadium, and the error vanadium,’o.7i to 0.85 could be avoided by boiling the alkaline solution for
M anganese, 0.08 to 0.14 2 O r 3 m i l l .
Copper, 0.04^ to 0.07 0— Uranium in the absence of vanadium would go Cobalt and nickel were added to Standard No. with cobalt and iron and be caught subsequently with 30a to give the percentages indicated in the table. iron in the ammonium hydroxide precipitate. In Expts. 5, 6, and 7 demonstrate conclusively the ac- the presence of vanadium, uranium would divide curacy of the method as applied to the determination between the sodium hydroxide filtrate and the pre-of cobalt and nickel. The data also show that the cipitate. In this case it would not interfere with the method satisfactorily provides for the determination cobalt and nickel determination, or with the chro-of manganese, chromium, vanadium, and copper, in mium and vanadium determinations if the electro-the presence of tungsten and molybdenum. metric or Johnson methods were employed.
COMMENTS ON THE METHODS SUMMARY
The following comments are worthy of note: I— This paper presents a method for the accurate 1— The method demonstrates that it is possible determination of cobalt and of nickel in cobalt steels, to separate, chromium and vanadium com pletely from The method is based on the electrodeposition of cobalt iron, manganese, nickel, and cobalt by a persulfate and nickel in a solution freed from iron, chromium, oxidation in acid solution, followed by tw o sodium and such interfering elements as tungsten, molyb-hydroxide precipitations performed by pouring the denum, vanadium, and copper.
hot acid solution into an excess of hot alkaline solution. II— Methods for accurate determinations of chro-2— Phosphorus and aluminium undoubtedly also mium, vanadium, copper, and manganese in the same quantitatively accompany chromium and vanadium. portion of steel are also provided.
June, 1921 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 543
REFERENCES
1— W . W . S c o tt, " S ta n d a rd M eth o d s of C hem ical A n a ly sis /' 2n d E d ., D. V an N o stra n d C o., 148.
2— A. A. B lair, “ T h e C hem ical A nalysis of Ir o n ,” 8th E d ., L ipp in co tt Co., 175.
3— C. M . Jo h n so n , "C h em ical A nalysis of Special Steels,” 2nd E d ., John W iley & Sons, In c ., 304.
4— Jo h n so n , Loc. cit., 307; B lair, Loc. cit., 180.
5— Jo h n so n , Loc. cit., 316; B lair, Loc. cit., 177.
6—J . W . R o th e, M itt. kgl. Tech. Versuchsanstolt zu Berlin, 1892, P a rt I I I ; B lair, Loc. cit., 177, 202.
7— I t is im p o r ta n t t h a t th e filter be n o t allow ed to ru n d ry , le st th e hydroxide coag u late an d re ta in tra c e s of v an ad iu m w hich would su b se
quen tly p re v e n t a satisfa c to ry d eposition of c o b alt an d nickel.
8— Sodium peroxide was em ployed in tw o p relim in ary experim ents for the oxid atio n a n d s ep a ra tio n of chrom ium a n d v a n ad iu m from iron, c o b alt, etc. A. A. N oyes, W . C. B ra y a n d E . B. S p ear [Tech. Quarterly, 21 (1908), 14], a n d also C. M . Jo h n so n [Chem. M et. Eng., 20 (1919), 588]. T h e sep a ra tion was co m p lete (E x p ts. 1 a n d 2, T a b le I I ) , b u t th e p ro ced u re was a b a n doned because i t w as necessary to re p e a t th e sep a ra tio n tw ice a n d th e p re cipitates were difficult to h andle.
9— F o r th e d e te rm in a tio n of ch ro m iu m a n d v a n ad iu m see page 541.,
10— T his p re c ip ita te rep resents a q u a n tita tiv e recovery of copper, an d th e percen tag e m ay , therefore, be d ete rm in e d b y ig n itio n to oxide or, preferab ly , b y electrolysis in a sm all volum e of solution.
11— I f m anganese is to be d eterm ined, th e p re c ip ita te should be dissolved in 40 cc. of n itric acid ( 1 : 3 ) , a n d reserv ed .
12— I f a d eterm ination of m anganese is desired dissolve a n y anode d e p o sit in th e solution described in preceding reference.
13— I f a d e te rm in a tio n of m anganese is desired a d d th e p re c ip ita te to th e so lu tio n re serv ed fo r m anganese (tw o preceding references.)
14— T h e fa c to rs for N iO , C oO a n d CojO« are 0.786, 0.787, and 0.734, resp ectiv ely . T h e use of th e fa c to r 0.75 on a p re c ip ita te w eighing 2 m g.
could, therefore, n o t occasion a n erro r g re a te r th a n 0.004 p e r c e n t on a 2-g. sam ple. W ith large p recip itates, ig n itio n to m etal in hy d ro g en m u st be carried o u t. Cf. T readw ell-H all, "A n a ly tic a l C h em istry ,” Vol. I I , 4 th E d ., p ag e 139, J o h n W iley & Sons, In c.
15— T h e re is no difficulty a t all in p re c ip ita tin g tra c e s of nickel in th e presence of a n y a m o u n t of c o b alt if th is m e th o d is followed. T h e precip i
15— T h e re is no difficulty a t all in p re c ip ita tin g tra c e s of nickel in th e presence of a n y a m o u n t of c o b alt if th is m e th o d is followed. T h e precip i