1469
V O L U M E 2 1 , NO. 1 2 , D E C E M B E R 1 9 4 9 549 mg. of manganese as manganese(l1) chloride. Atti-niph t i ) shorten the procedure through an extraction of cobalt l-nitroso2-naphtholate in chloroform resulted in no improvement, as the very stable cobalt complex was not extracted from the chloroform phase with strong acids and was not completely decomposed through oxidation by hot concentrated sulfuric or nitric acids. Evaporation of the chloroform followed by the above ashing procedure resulted in 100% recovery of cobalt but required morr time than the filtration procedure. The chloroform extraction technique may find application when the aqueous phase is also to hr. analyzed. Copper in large amounts was found to interfere because of its piior reduction a t the dropping mercury electrode. In ammoniacal solution copper(I1) ion is reduced stepwise with half-wave potentials of -0.23 and -0.50 volt (S.C.E.). It should be posi h l e todeterminesmall amounts of copper simultaneously with cobalt by the present procedure, or the copper could be separated b \ classical electroplating procedures. The authors studied a 3impIe procedure of reducing the copper to the free state by zinc. One gram of zinc dissolved in 5 ml. of mercury was added to a wlution of the sample in about 50 ml. of hydrochloric acid having a concentration range of 0.5 to 6 LYand the solution was heated near 100” C. for 5 minutes after the last trace of blue was observed. The samplcs contained 29.5 mg. of cobalt and 0.1 to 0.5 gram of copper. As much as 17% of the cobalt was deposited along with the copper in samples containing 0.5 gram of copper, but less than 1% of the cobalt was deposited if the amount of copper was rcduccd to 0.1 gram. Thus, this simple procedure can bc used to remove copper from samples containing less than 0.1 gram of copper. Chromium interferes, because i t is oxidized to chromate ion u hich is reduced to chromium(II1) before ammino cobalt(II1). The interference of chromium is readily eliminated by adding a slight excess of 1 M barium perchlorate following the oxidation but before diluting to exact volume. Vanadium and molybdenum do not interfere, because the half-wave potentials of vanadate and molybdate in the electrolysis medium are more negative. SUMMARY
.Ipolarographic procedure for determining cobalt as the cobalt ; H I ) ammine is described. A new method was developed for obtaining rapid and quantitative oxidation of cobalt(I1) to cobalt 1111)ammine with elimination of the excess oxidizing agent,
.utlium perborate.
The polarographic procedure is parric-ultirl\ iieeful for determiriing cobalt in nickel compounds or iii rhr electrolytically deposited mixture of cobalt, nickel, and l i n t uhirli do not interfere. The amounts of iron or manganese in the final solution must not exceed that of cobalt which is partially coprecipitated with the IIJ drous ferric oxide and the manganese dioxide, the latter being for the re:ormed during the oxidation with perborate. The duction of copper to the univalent state which precedes the cobalt (111) JTave can be used for the simultaneous determination o‘ ‘opper and cobalt hut interferes if copper is present in a l a g r wresb Chromium interferes because it is oxidized to chromate which i3 polarographically reduced to chromium( 111) at nearl: the same potential as cobalt(II1). Vanadates and molybdate5 which are formed during the oxidation do not interfere, as their waves occur at more negative potentials. Simple procedures fur Yepnrating interfering elements u-hich were tested and found satis:actor?- include the isopropyl ether extraction of ferric iron, the 5eparation of copper with zinc amalgam, and the precipitation of nhromate as barium chromate. For the separation of cobalt frorr manganese, 1-nitroso-2-naphthol is Ratisfartory BIBLIOGRAPHY
,
1) Bjerrum, J., “Metal .Immine Formation in Aqueous Solutlm,,
(in English) Copenhagen, Denmark, P. Haase and Son, 1941
(2) Brdicka, R . , Collection Czechoslov. Chem. Commun., 5, 112 (1933; i3) Dodson, R . W., Forney, F. J., and Swift, E. H., J . Am. (‘hem Soc., 58, 2573 (1936). 4) Engle, W.D., and Gustavaon, R. G., J . Ind. Eng. Chem., 8, 901 (1916).
,5) Evans,B. S., Analyst, 50, 389 (1925).
:6) Hillebrand. W. F., and Lundell, G. E. F., “Applied Inorganic Analysis,” New York, John Wiley & Sons, 1929. 17) Kolthoff, I. M., and Lingane, J. J., “Polarography,” New York Interscience Publishers, 1941. 8) Laitinen, H. A , , Bailar, J. C., Jr., Holtrclaw, H. F., and Qiianiiano, J. V., J . Am. Chem. Soc., 70, 2999 (1948). (9) Lingane, J. J., ISD.EXG.CHEM.,ANAL.ED., 18, 429 (1946 10) Metzl, A., 2. anal. Chem., 53, 537 (1914). ‘ 1 1 ) Tomicek, O., and Freiberger, F., J . Am. Chem. Soc., 57, 801 (1935). (12) Willis, J. B., Friend, J. A., and Mellor. D. P., Zbid., 67, 1686 (1945). RECEI\LD June 8, 1949. From a Ph.D. thesis by James I. Watt--,
I-n
vrrsit?: of Wnneqota, 104:1
Determination of Acetylene and Monosubstituted Acetylenes .J. GORDON H i N N A
4ND
SIDNEY SIGGIA, General Aniline Film & Corporation, Easton, Pa.
A method has been developed for the determination of those compounds which where R can also be a hjdrogen atom. The contain the grouping R-C=CH, method has definite ad\antages over others fnr these cnmpoiinds. and is rapid and precise.
A
CE,TYLE:h h has been determined colorimetrically \3 1th 110svay’s solution (3,9),but the red color of the cuprous acetylide darkens in the presence of oxjgen and other impurities through oxidation The explosive copper acetylide may be dried and Relghed ( 7 ) , or the copper may be determined by any stmdard method and the acetylene estimated. The use of cuprous ion in acetylenic compound determinations has several disadvantages The cuprous solutions deteriorate rapidlg, the cuprous ion oxidizing to cupric. The precipitate is not conveniently analyzed, brraiiw it is explosive, making gravi-
:iietric determination difficult though possible. The determinatior of copper in the preripitate is the preferable method, but this is time-consuming. Other methods ( I , L ) are h a d on the estimation of acetylene ,)r acetylide by titration of the nitric arid liberated from a neutral d v e r nitrate solution according to the equations:
.H
-(
q H + 3h4S0j I ~ A k g - = ~ 1 .2; i,g ~ \ ; o 3 + ~ H Y ( , CH=-C CH=CHZ 2AgSOs + ( C i;-+C CH--=CHz) AgXQ A H \ ( +
+
)I
1470
ANALYTICAL CHEMISTRY
Sovotny ( 5 ) proposed that the silver in the precipit:ito I)(, ( i t \ rerniined. The disadvantages of using silver ion are mainly due to thr interference of any halides, cyanide, sulfides, and traces (down t80 0.01%) of aldehydes in the sample. These interferences vonsume 4lvei. ion, the halides and sulfides by precipitation of t,htJ silver d t s , the cyanides by complex ion formation, and the aldehydes I)y reduction of the silvtar ion to niet:tllic silver. Traces of aldt~liydes affect the deteruiinntion of the nitric acid liberated t)y the 4 v e r nitrate (1, Z), Foi, tlie nietallic silver formed obscurrs tht' r ~ n point d completely. Sriittll :+mount,sof aldrhydes (up io 0.59 :L.* formddehyde) cttn lw t o k m t d in the procedurc l)c,low. 1 !nwver, because aldr.hydc+ arc' oxidized by the potassium mt?rvuric iodide, amounts larger than 0 . 5 9 will begin t'o affect th(h rtcetylenic hydrogen result P. Wellers (10) absoi,bed thc #:in in slightly alkaline solutions of ium mercuric iodides. .-\wtylene has also been estimated by lining the mercury in tlir :icet,ylide precipitate ( 4 ) by tit,rating with ammonium thiocy:tn:rte by the method of Volhard. FIX purposes, Shriner and Fuson (8)reconiin mercuric iodide t o form the mercuric. $(lerivative of those c~ornpouritis whirti rontain the grouping -C'=CH, according to the formula:
2lfor hoth opaqiir and clear liquids. The sample stream flowwntiriiiousl), and ma? he under pressure. Good stability has been achieved w i t h a maximum sensiti\it> of *0.00005 refractive index unit. The action depends on intensity of internal reflection. near the critical angle, in a prism i n routact with the sample streani. iist.,
R
t~:E'RACTIVh; iritirx has long been recognized :ts it funclamental propert>-of niiittrr, but in spite of its long usage as :i itleasure of chemical purity it has fuund little :ippIiratinn HS :I meiiiis of process control in clic.mica1 industry. Thrrc. are basically t v Y J types of refr:ictivtl index nie~murenient~ in gcnwil use: One depends on refraction of light :it the h o u n d a ~ y Iwtween the sample and N rrfrrcnce medium, rind t h t s ot1ic.r tic ] ) t w d s upon the form:triori of' iiitc~rfcwrricefringes t o rstim:itr thv 1.fftvtive optical path length. It has heen long knowri :ind recent.ly emphasized (3)t h t rvI r:tctive indexes of substan *re correlated with the iiiitwsity 01' Itle reflected compontwt of light impinging on a pri,sm-s:tnipl(~ I)oundary. For a fixed angle o f incidenc~the intrwsilg of tlie ribficlcted light is dependent upon the ratio of refractivcr indtsxcas of t h r I h n i and the liquid. If the reflected light is converted into an (.lectric:il signal, this principle Imniiir~siisahle in continuously ril.(.I )rding instrument s. This method may t)r t:xploitc~l1 ) ~ either :t single- or niultipleI
I'ri.+nt
address, Comiuercinl So1rc~nt.iCorporation, Terre Hantc. Ind.
I efle(*tiwi t echiiiquc. The aiiigle-rc~flc~ri io11 pnn(vpk m:&y be utilizrtl by a trapezoidal prism as shown in Pigirrt* 1 and the multiple-reflection one by a glass rod as shown in Figurr 2 ( 2 ) . This papcr is concerned with the application of tlie single-reflwt itjri technique to n continuously recording refr:rrtoinrtrr
THEOHl OF I N S I R U M E h T
111 I'igui.c. 1 :I parttllcl beam of light i3 reflected f r o i i i ,I gldsb-nniple boundary. If the :ingle of incidence is less th:tn the miticd, the amplitude of tlir reflected light will depend on the dirrctiori of polarization o f the incident light, on t h r :tngle of incidence, aiid on the ratio of refractive Indexeq of the #la sninple. 1 - s ~rnn be ni:tde of Fresnel's equations ( 1 ) where the amplitude of :L reflected ray of light, the incident light being polarized normal t o the plitnp of incidrncc arid of unit :implitude, i.; in the notation nf Figurr 1
