ANALYTICAL CHEMISTRY
944
Table 111. Vanadium Analyses in Presence and Absence of Uranium Aliquot Soh. 1
V Present
No. of Detns.
11.11.
.lly.
1.00 2.00 3.00
1.78 3.56
3 2
5 ,:34
3
S o h . L' 3.00 2.00 1, 0 0 0.500
0.300 0.200 0,100 0.060
V Found, h'o Cranium
v Follnd, Grains U Preaent
$
xg. 1.78 ?.52
XO.
1.78 :I 5 2 3 34
1-1.5
S o . of Detm.
3
J
Standard Deviation
% ,... . . ,
33
.
,
the vanadium is necessary, because the iron present from the initial titration does not cause difficulty.
SiIsxirn~ini Deviation
74 ..,
..
ACKNOWLEDGMENT
The authors acknowledge the helpful suggestioris of L. P. Pepkowitz and of E. L. Shirley with regard to use of the microburet.
1 3 Grains
U Present
n
3.62 2.41
, .
1.21
0.60 0.36 0.24 0.12 0.07
.. , .
..
3 63 2.43 1.20
5 3
0.fil 0.36 0.25
1
h
3 3
ri 23
0.4i 0 . 3$1
0.10 0 . (18
0.i4 1 2
1.6
.. ..
0.31 0.58
0.74 0 85 1 3 2 0
.. ..
LITERATURE CITED
(I) Boaz, S u m e r o f . P r o t a t a , a n d Throckniorton, "Chemical and Spectrochemical Analysis of U r a n i u m arid Plutonium M a t e r i a l s , " Atomic E n e r g y Commission, DccZassi$ed Document MDDC 279 (194G). (2) Claassen aiid Corbey. Rec. t m o . chim.. 67, 5-10 (1948). ( 3 ) Cooper and )Tinter. :iN.IL. (:HEM., 21, 6Oj (1949). ~I
of the potentiometric method compared favorably with the deadatop procedure; however, the rapidity and ease of the dead-stop procedure have much in their favor, especially in the presence ol' excess uranium. In Table I1 are show11 data for recoveries of vanadium in the presence ol 10 mg. of chromium and 10 mg. of t,it,a.niumas ivcll as excess of uranium. These elements are t,wo that frequently occur in Janiples analyzed for vanadium. It is apparent that as much as 10 mg. of chromium or titanium will not interfcre in t,hc determination of milligram quantities of vanadium. Table 111 contnins data for recovc:ics oC vnnadium in the mngc of 5 to 0.10 mg. The largest single i l tion has n value of -I.S", u-hcn 0.44 mg. of variadiunl is prescnt. Iri the usual sample cont.aining approsimatcly 2 mg. of van:ltliurn, the niilrimunl tiwintion was less than 0.67, arid the average deviation in several samples will be considerably less than thjs?:tmount. When this deviation is considered in terms of a sample containing an escess of uranium, the result is much better than can be utilixed. The method is applicable to the usual source materials containing vantttiium arid uranium and to samples corit,aining no uranium. One sample may be run several times by this method: only a reosidat,ion of
(4) Decret. Anal. Chinz. Acta,, 1, 135-4 (1947). (5) Foulk a n d Rawden, .J. Am. Chern. SOC.,48, 2045 (1926). (6) Furman, Ibid., 50, 1675 (1928). (7) Hillebrand a n d Lundell, "Applied Inorganic Xiiaiysis." p. 61, New York, John .\Viley & Sons, 1929. (8) Kolthoff a n d Yandell, IND.ERG. & m . . ANAL. Eu., 2, 140-5
(1930). (9) Kolthoff a n d Toinicek, Rcc. t m i i . chinz., 43, 447 (1924). (IO) Kroupa, Edith, M i k r o c h e m i ~W T . M i k ~ o c h i r n . Acta, 32, 245-51 (1944). (11) L a n g a n d Kurz, 2. mad. Chem., 86, 288-:103 (1931). (12) Mitchell a n d Smith, "Aqunmetry," 11. 86, Kew York, Int,erscience Publisbcrs, 1948. (13) Pepkowita a n d Shirley, grivat,e cooiniunication from L. P. Pepkoivi tz. (14) Stock, Metnllurgia, 37, 220-3 (1948). (15) Strock and Drekler, .I. O p t i (16) Willard and Gibson. ISD. 1.. E D . , 3, 85-93
(1931). (17) Willard a n d Young, I h ' d , 6, 48-51 (19314). (18) W r i g h t a n d Mellon, I?>id.,9, 251 (1937). (19) Ibid.. p. 375. RncEIvsn Se[!telnher 29, 1949 W o r k rsr:ied Eng. 52, Atoiiiic Energy Commission.
olit
iinder contract 1$'-31-109
Separation and Determination of Cobalt in Presence of Nonvolatile Radicals Use of Quuternury Ammonium Hydroxides A Y D TIIO.1;IAS P. h1CCUTCHEO.V University of Pennsylvania, Philadelphia, Pa.
LOUIS C. W. BAKER
OBALT may be weighed accurately as cobalt sulfate followC ing ignition a t not over 550" C. When only volatile or ashless ions or molecules are present, cobalt may be deter( 6 , ?).
mined by evaporating to dryness with a little sulfuric acid and igniting (6). When nonvolatile radicals are present, cobalt is frequently separated by precipitation with a strong base and an oxidizing agent. Because the precipitated cobaltic hydroside always occludes some of the alkali (4)and some of the other nonvolatile component,s of the solution, high results are obtained if the cobaltic hydroside, even though very thoroughly washed, is converted to cobalt sulfate for weighing. The procedures available for accurately estimating cobalt in these cases involve special equip-
ment or techniques which lack the simplicity and elegance of the sulfate method. The purpose of this paper is to show that by substitut,ing the readily available, strong, ashless quaternary ammonium hSdroxides for the alkalies, precipitates are obtained which can be converted quantitatively to the sulfate for accurate weighing. When nonvolatile constituents are present,, the cobaltic hydroxide must be dissolved again and reprecipitated to avoid occlusion of traces of nonvolatile substancrs. Sodium hydroxide may be used for the first precipitation. Bromine water may not be used as the oxidizing agent in the precipitation with the quaternary ammonium hydroside, because these reagents form orange precipitates, probably perbromides ( 2 ) ,when mixed.
V O L U M E 2 2 , NO. 7, J U L Y 1 9 5 0
-
Table 1. Determination of Cohalt in [CoCI (Co Section
A
R
C
Results,
23,52
23.60 23.53; 23.57
23.5i
23.75
21.23
25.08
r)
23.53 23.56 23.59
CI:
23.53% by theory)
ilverage, 4’0
23.50 23.52 23.54
23.87
945
23.56
Mebhod Evaporating w i t h HxSO,. Weignin:: as COS04 I n presence of an equal number of moles of EIzCrO4 and of KazWOt: precipitating Co!OH). with HvOo and ?;aOW. redissdving, and-precipitating with HzOz and trimethyibenzylrtmmonium hydroside. Weighing a8 cos04 Precipitating Co(0H)s with HlOz and XrtOH. Washing with 500 ml. of hot water. Weighing as cos04 Precipitating C,o(OI-I)r with HzOg and triniethylbenzylammonium hydroxide. Washing with 20 mi. of hot water. Weighing as CoSOi
EXPERIMEN’I’A L
Chloropent,amniinecobaltichioridewils choscn as the source of cobalt in all the experiments described, because this compound can be prepared readily in a pure state (1). A sample of this salt, weighing approximately 0.6 gram, was used for each of the analyses listed below. This weight produces 0.37 gram of cobalt sulfate. 4. Cobalt was dci.ermined in cach of three samples by the sulfate method. The results are listed in sect,ion A of Table I. B. Each of three samples, weighed out, into a 50-ml. beaker, was dissolved, with warming, in 20 ml. of water and treated as follows: A solution (10 ml.) was added which contained the same number of molw of potassium chroma.te and of sodium wolframate as t,lw number of moles of salt, in the sample. (The orange colored chromatc and wolframate of the cobalt’ammine cation were precipitated.) -4 little macerated Whatman‘s S o . 42 filter paper lyas added a s a filter aid. The liquid n-as hcated to the boiling point, and removed from the heat source, aiid 1 ml. of 3% hJ-drogeri peroxitlc solution was added, followcd by 5 ml. of 3’3: sodium hydrosidt solution, added cautiously beneath the watch glass from 11 pipet, i n order 00 decompose the salts and preripitate cobaltic hydroxide. The mixture was stirred and, a i ’ t h effervescence had ceased, boiled gently on a hot plate for a short time, after n-hi the precipitate was a l l o ~ e dto settle. While still warm, the m t,ure W L S filtered with gentle suct)iori through a glass sealing tUiJe 10 mm. in diameter containing a medium-fineness fritted-glass disk. Previous to this filtration, a suspension of macerated filter paper had been filtered through the sealing tube, so that a moderately loose mat of paper pulp, approximately 4 mm. thick, lay on top of the fritted glass. The mat was washed with a little dilute solution of the same base that tvas used for the precipitation (sodium hydroxide in this case) before filtration of the cobaltic hydroxide. The filtrate, acidified with hydrochloric acid and heatc.d, was tested for cobalt with negative. rcsult,s. The precipitate, which was never sucked dry until washing was complete, was washed with about 40 ml. o first been used to rinse the beaker. Aft~er been drained from t.he precipitate, the s connected, and t,he lower parts of the sealing tube washed, the beaker n-as placed beneath the t,ube and about 2 nil. of hot concentrated hydrochloric acid -were added a t t,he top of the sealing tube. The dissolut,ion of the cobaltic hydroxide was facilitated by cautious warming of the outside of the sealing t,ube wit~ha very low flame. The resulting solut,ion was blown through the sealing tube by gentle air pressure applied at the top, and the sealing tube was washed once with a little water. The exceSs hydrochloric acid was evaporated by placing the beaker on the hot plate. Toward the end of this evaporation, a watch glass was placed on the beaker and 0.5 mi. of concent,rated nitric acid was added to h r o y the suga.r from the filter paper. When the slight effervescence had ceased, the watch glass was rinsed into the beaker and it was replaced beneath the sealing tube. The remaining traces of cobaltous chloride were washed from thc tubc int,o t,he beaker with small portions of hot, water. The filter paper remaiuing in the sealing lube was colored light Yellow by a little wolfram trioxide from u-olframat,es which had been occluded in the precipitate. A trace of this wolfram trioxide m h c d through into the cobaltous chloride, but was separated by
t.he second precipitation. The filter paper remaining after this latter precipitate had been dissolved was pure whit,e. Macerated filter paper and hydrogen peroxide were again added exactly as before; and, after dropwise neut’ralizationwith a 2.5 N aqueous solution of trimethylbenzylammoiiium hydroxide (Triton B, Rohm & Haas Company), the procedure was followed exactly a s previously described, except that the 2.5 N trimethylbensylammonium hydroxide was substituted for the 3 N sodium hydroxide solution, and that it was unnecessary to fume off t.he excess hydrochloric acid before thoroughly washing the cobaltous chloride from the sealing tube. When the cobaltous chloride had again been transferred to the beaker, 0.5 ml. of concentrated sulfuric acid was added, and the beaker was placed on the hot p1at.e. The solution was evaporated to about 3 ml., and covered with a watch glass, and 1 ml. of concentrated nitric acid was added to aid again in the dest,ruction of organic matter. After the effervescence had ceased, the solution was transferred to a 15-ml. porcelain crucible and the content evaporated, using a low flame applied to a miniature air bath made from a large crucible. The beaker and watch glass were washed xith small portions of hot water and the washings iwre added periodically to the crucible ns evaporation progressed. After a full Bunsen flame failed to produce more visible sulfur trioxide fumes, the crucible was allowed to cool, and 2 drops of water were added to aid in the expulsion of the last traces of sulfur trioxide (3). The content of the crucible was evaporated to dryness with a low flame as before and hea,ted a short t,ime on the air bath with full Bunsen flame. The crucible and cont,ent were ignited to const,ant weight (approximately 25 minutes) in an electric muffle furnace a t 550’ C. The residue was weighed as cobalt, sulfate. The results are list,edin section B of Table I. Tetraethylammonium hydroxide was used qualitatively with every indication of equally satisfactory results. Commercially aviiilable quaternary ammonium hydroxide solut,ions have Ere quently been stored in soft-glass bottles and therefore contain appreciable quantities of silica. It is most important, in applying this method, that a little of the base be ignited to ascertain t,he amount of nonvolatile impurities it, contains. If no ashless base is available, i t may be prepared conveniently from a solutrion of a quaternary ammonium salt, which usually will be free from silica, by ion exchange using Amberlite IRA400 (R.ohm &- Haas Company). The following experiments were performed in order to contrast the effects of the use of sodium hydroxide and of quaternary ammonium hydroxide bases in precipitat,ing cobaltic hydroxide.
C. Each of three samples, containing no chromate or wolframate, was precipitated once with hydrogen peroxide and 3 N sodium hydroxide solutions, filtered, washed, redissolved, evaporated, and weighed exactly as described above, except that 500 ml. of hot water were used to wash the cobaltic hydroxide instead of 40 ml. The results, all high, are listed in section C of Table I. D. Each of thrce samples was treated exactly as in part C except, that’a 2.5 11; aqueous solution of trimethylbeneylanunonium hydroxide was substitut,ed for the 3 A’ sodium hydroxide and only 20 ml. of wash wat,er instead of 500 mi. were used. The results are listed in section ll of Table I. LITERATURE CITED
(1) Bilts,
€I., and Biltz, W.,“Laboratory Methods of Inorganic
Chemistry,” 2nd ed. (adapted from German by W, Hall and 9. Blanchard), pp. 173-4, h’ew York, John Wiley B: Sons,
1928. (2) Chattaway, F. D., and Hoyle, G., J . Cliem. Soc., 123, 654 (1923).
(3) Ilillebrand, R. F., and Lundell, G. E. F., “Applied Inorganic Analysis,” p. 325, Yew York, John Wiley B: Sons, 1929. (4) Treadwell, F. P., and Hall, W.T., “Analytical Chemistry.” Vol. II,8th ed., p. 345. New York, John Xiley 6: Sons, 1935. (5) Ibid., p. 146. (6) Willard. H. H., and Diehl, H., “Advanccd Quantitative .4nalysis,” p. 381, New Sork. D. Van Kostrand Co., 1943. (7) Willard, H. H., a.nd Hall, D., J . Am. Chem. Soc., 44, 2231 (1922). RECEIVED Augunt 2 5 , 1949.
Gorrect io n In the nrticle on “Rapid Routine Calculation of 33ulticomponent l\’Iixturc.s with Punched Card Machines” [Opler, Xscher, ANAL.CIimf., 22, 559 (1950)l in the second column, step 2, thc number under “3” should be 280, not 589 as printed.
