April 15, 1941
271
ANALYTICAL EDITION
Acknowledgment
Literature Cited
The authors wish to acknowledge their indebtedness to E. W. R. Steacie, of these laboratories, who built the buret, and to D. J. LeRoy, also of these laboratories, who filled the buret with the various gases analyzed.
(1) Niederl, J. B., and Niederl, V., “Micromethods of Quantitative Organic Elementary Analysis”, New York, John Wiley & Sons, 1938. (2) Pregl, F., “Quantitative Organic Microanalysis", Philadelphia, P. Blakiston’s Son & Co.. 1930. PUBLIBBED as N. R.C. No. 953.
Interferences Occurring with Selected Drop Reactions LOTHROP SMITH AND PHILIP W. WEST’ State University of Iowa, Iowa City, Iowa
A
S A G E N E R A L rule drop tests and other color reactions
are developed especially for use for specific tests. There are, however, few truly specific reactions and there is need for information concerning such interferences as may occur and steps that may be taken to remove them. Systems of semi8, 10) i n microqualitative analysis have been developed (1, I, which spot tests are used for the identification of the different ions after the usual group separations. Gutzeit (6), Krumholz (4),and Heller (6) have proposed schemes of qualitative analysis based on the more simple separations. The interests of the authors have been more closely allied to those of the latter group of workers, and a system of analysis has been developed (9). Special consideration has been given t o the adaptation of this system t o use in portable kits. In the system employed by the authors. a two-group separation of the elements under consideration is used. The first step is either fusing the sample with sodium carbonate and sodium peroxide, or adding sodium carbonate and then sodium peroxide to a solution of the unknown. In either case, the water-soluble carbonates and hydroxides are separated from the insoluble oxides, carbonates, hydroxides, etc., by filtration. This accomplishes a n almost equal division of the more common elements into two major groups. One of the main advantages of this procedure is that oxidation by sodium peroxide yields the elements in a constant state of oxidation, usually the highest. This adjustment of valence has two main advantages: (1) since all forms of a n element are converted to one common valence, many tests are eliminated; (2) the elimination of extra valence forms reduces the number of possible interferences. When this procedure was first investigated, no study of interferences was made. Instead, the interferences listed by Feigl (3, 4)were noted, and the effect of the proposed separation procedure in eliminating these interferences was taken into account. Throughout 4 years of observation and use the two-group separation has proved to be of great value in conducting microchemical analyses by means of drop tests. In the course of this work i t has been observed t h a t there are a considerable number of interferences not listed in the general literature on drop reactions. For this reason the investigation on which the present report is based was undertaken.
Solutions and Reagents For the study of interferences, solutions were made up to contain approximately 5.0 mg. per ml. of each element to be studied. 1
Present addresa, Louisiana State University, Baton Rouge, La.
I n the preparation of each such solution, an appropriate amount of the c. P. chemical was fused in a platinum crucible with sodium carbonate and sodium peroxide. The melt was then dissolved in water, the pH was ad’usted to a value as near 7.0 as possible, and the solution was boded to decompose the remaining hydro en peroxide. After being cooled, the solutions were made up to b e re uired volume and placed in convenient Pyrex dropping tubes. this procedure, solutions were prepared for lithium, sodium, potassium, copper, silver, gold, beryllium, magnesium, calcium, zinc, strontium, cadmium, barium, mercury, boron, aluminum, carbon, silicon, titanium, zirconium, tin, lead, thorium, nitrogen, phosphorus, vanadium, arsenic, antimony, bismuth, sulfur, chromium, selenium, molybdenum, tungsten, uranium, fluorine, chlorine, manganese, bromine, iodine, iron, cobalt, and nickel. Only one solution was needed for each element, irrespective of the number of variations in valence in which it occurs, since the action of the sodium peroxide in the preparation of the solution leaves each element (except manganese) in a single state of oxidation, usually the highest. I n the case of manganese, a fresh known solution was made up each day, since the solution gradually decomposed to give variable mixtures of manganese dioxide, manganates, and manganous salts. The reagents and apparatus used in this work have been described previously (9).
8y
Method of Studying Interferences The actual investigation of interferences was carried out according t o a definite scheme. Because of the varied forms of phosphate interference met with, special attention was paid to the behavior of this ion under each set of conditions studied. The following series of solutions was prepared and used in studying the interferences with each test. 1. Blank 2. Element under consideration 3. Element plus phosphate
Individual members of periodic group I, in the absence of the element to be studied Individual members of periodic group 11, in the absence of the element to be studied, etc. 5 . Individual members of periodic group I lus element Individual members of periodic group If plus element, etc. 6. Individual members of periodic group I plus phosphate, in the absence of the element Individual members of periodic group I1 plus phosphate, in the absence of the element, etc. 7. Individual members of periodic group I plus phosphate plus element Individual members of periodic group I1 plus phosphate plus element, etc. 4.
The interferences found were reported as positive if a false test was obtained in the absence of the element sought, and negative if the test failed to indicate presence of the element
INDUSTRIAL AND ENGINEERING CHEMISTRY
272
Vol. 13, No. 4
TABLEI. ANALYTICAL PROCEDURES AND FIXDISGS Element A1
Sb
As
Procedure Spot plate 1. 1 drop of soln. 2 . 1 drop of 0.1 N NaOH 3. 1 drop of alizarin S 4. 2 drous of acetic acid Orange COG A . Watch glass 1 . 2 drops of soln. 2. 1 drop of (NHdzS 3. 1 drop of concd. HC1 4. Remove excess liquid 5. 1 drow of concd. HCl Warm B. Filter paper 1. 1 drop of phosphomolybdic acid 2. 1 drop of soin. A 3. Hold in steam Blue stain Gutzeit apparatus A. Place in body of ap-
Interferences Listed Feigl (9,4) Lange (7) Interferences Found" Aqueous Group Fe, Cu, Co, alFe, Cr. Co, Mn kaline earths, Cr
Sn++
Sb,
S--.
Pod---
Au(-), Ag(-), B a ( - ) , Hg(-), P b ( - ) , Bi(-)
1. A E,",u,"ins of z n 2. 1 ml. of 0.1 N HC1 3. 4 drops of SnCl4 4. 2 t o 4 drous of test
Be
B
CI
"I+,
Spot plate 1. 1 drop of soln. 2. 1 drop of 0.1 N HC1 1 droD of fresh starch 3. .~ pas'te (cold) 4. 1 drop of KNOn Blue color
Test
Interfering ions slow up reaction but by adding fresh Zn a t intervals and allowing reaction to proceed 20 minutes o r more test is specific for qualitative work.
1 drop of K C N will mask Cu, Ag, and Au interferences. 1 ml. of Br? water fades color due t o Mg but not t h a t due t o Be. Test is inconclusive in presence of Cd and Ba.
Cu, Ni, Fe Mg tartra'tes in'presence of aluminum
Casserole 1. 1 drop of s o h . 2. 1 drop of concd. HC1 3. Evap. t o dryness 4. Dissolve in 1 drop 5 N NaOH 5 . 1 drop of quinalizarin Blue color Glass spot plate 1. 1 drop of turmeric 2. 1 drop of s o h 3. 1 drop of 0.1 N HCI 4. Evaporate t o dryness 5. 1 drop of 5 N NaOH Greenish-blue color (momentary) Chloride apparatus A. Place in ignition tqbe of apparatus 1. Suitable amount of dry sample 2. Few grains of K2Cr01 3. 1 drop of concd. HZSOI B. Place 1 drop of fresh diphenylcarbaeide in reaction capillary C. Warm ignition tube Pink color in reaction capillary Spot plate 1. 1 drop of sbln. 2. Acidify (HzSOI) 3. 1 drop of diphenylcarbazide Pink color Spot plate 1. 1 drop of soln. 2. 1 drop of 0.1 N,HC1 a. 1 drop of Zr-alizarin soln. Pink reagent fades t o yellow
Test drop should be alkaline prior t o addition of alizarin S. Final should be less than 4.0. After N a d ? NazOr separation. V, Mo, and Cr are only interfering elements present, (NH4)zS separation yields Sn in stannic condition which does not interfere, thus making test specific.
Not listed
Not listed
Remarks
Oxidizing agents, 1-
PO4 ---, Si,O!--, oxidizing agentd
Many ions ive red colors with turmeric b u t only 3! and Au stains turn blue upon addition of NaOH. N a z C O r Nan02 separation eliminates all interferences except those due t o POI--Si, Be, V, Cr, and Mo, all of which tend t o inhibit test
Ag, Hg, NO?-, Br, I, F
Not listed
TeRt is inconclusive in presence of Ag Hg and F. Very large amts. of I and Br 'mask test.
Fe does not interfere
V and M.0 are only interfering elements appearing in aqueous group. Mo interference ma be eliminated by adding 1 drop of o&c acid t o test drop.
(I
Cr
F
I
Mo
Filter 1. 2. 3.
pa er 1 &op of concd. HCl 1 drop of soln. 1 drop of KCKS 4. 1 drop of SnClr Red stain on edge of spot (not faded by SnCL)
P
Spot plate 1. 2 dro s of ( N H 3 r Mo&
Be(-) Al(-) Si(-), T h ( 1 ) . S b ( L ) , S(+), Cr (masks)
inhibited alum al: kali sulfate, cyanides and c&+n organic compounds Sensitivity reduced by ECHO,H+'OI, organic acids. Hg salts, nitriles
!?gsod.
Si, As
Specific within acid group.
Interferences not mentioned
Not listed
Interferences not given
Zr and T h appear in other group. S (801--) may be removnd b y adding 1 drop of BaCh and filtering off Bas04 p p t . Be,.Al, Si, and Sb suppress test if present in large amounts.
Au Fey$,
color),
Se(+),
W (blue stain)
Si(+), As(+)
Stain due t o Au turns purple when S n C h is added. Red stain due to Mo !i carried past any blue Au or W stain b y capilrary action. This capillary. m o v e ment of Mo stain also differentiates it from red Se stain which. is insoluble in HCI and therefore remains a t center of spot. A specific test. All interferences are eliminated by adding 1 drop of concd. HCI evaporatin t o dryness, and extracting with HfiOi.
April 15, 1941
273
ANALYTICAL EDITION TABLE I (Continued)
Element
P (Con't)
Procedure
Interferencea Listed Feigl (9, 4) Lange (7) Interferences Found" Aqueous Group(Con't)
1 drop of s o h . 2 drops of HNO; 1 drop of SnCh Blue color 2. 3. 4.
K
Rrmarks Extract will contain only PO,--- as As distills off as chloride and Si is converted t o insoluble SiOz. Si interference alone may be prevented by adding small crystal oi tartaric acid t o (NHdnMoOd drop. Lithium interferes. Lead gives yellow ppt. soluble when heated, thus differentiating it from Li ppt,
Spot plate (black) 1. 1 drop of s o h . 2. Evaporate t o dryness 3. 1 drop of acetic acid 4. Few grains of sodium cobaltinitrite Yellow ppt. Spot plate 1. 1 drop of s o h . 2. 1 drop of thiourea 3. 1 drop of "Os Red color
Li, TI, NH4+
Not listed
Cu, NO:-, Te (yellow ppt.) BI (yellow! PPt.1
NO:-,
Casserole 1. 2 dro 8 of (NH4)nM084 2. 1 drop of soln. 3. Warm, cool and filter from ahy visible ppt. of (NHi)rPO4.l2MoOs 2 drops of oxalic acid 4. 5 . 1 dron of SnClz Blue color ' A. Watch glass 1. 2 drops of s o h . 2. 1 drop of (XHdzS 3. 1 drop of (NHdzCOa 4 . Filtef B . Spot plate (black) 1. Filtrate A 2. 2 drops of acetic acid 3. 6 to 8 drops of zinc uranyl acetate Yellow ppt. (allow 5 minutes t o form)
asoa---
p04--480,L-
None, except in very concentrated solns.
POa;--, proteins, large amounts of K
Ti(-)
None
N o t listed
V ( + ) , Sb and As gave ppts. which masked test, Cr (masks)
If V , Sb. As, or Cr is present alternate procedure such as BaCI? test (carried out on hlark @potplate) should be used.
Watch glass 1. 1 drop of s o h . 2. 1 drop of (NHdzS 3. Absorb excess liquid 4. 1 drop of concd. HC1 5 . Add few grains of powdered Mg and heat until hlg dissolves B. Filter aper 1. 1 tirop of soln. A 2. 1 drop of phosphomolybdic acid Blue stain Filter paper 1. 1 drop of concd. HC1 2. 1 drop of soln. 3. 1 drop of K C N S 4. 1 drqp of SnCh Blue stain in center of spot
3b
Not listed
Sb(+)
If Sb is ahsent proceed from B. sperifir.
Mo, HaPO4, certain organic hydroxy acids
Not listed
.4u (red stain changing t o
Specific when attention is paid t o color and position of stains. Au and W both give blue stains in center of spot but Au gives a preliminary red stain upon addition of KCNS while W does not,
V
Filter 1. 2. 3.
paper 1 drop of aniline 1 drop of HNOa 1 drop of soln. 4. Warm Green stain
Xot listed
N o t listpd
Ba
A.
Watch glass 1. 2 drops of s o h . 2. 1 drop of (NHdnS 3. Filtef B. Filter aper 1. I Brop of filtrate A 2. 1 drop of 0.1 N HCl 3. 1 drop of sodium rhodizonate fresh) 4. Let Stan6 until color develops 5. 1 drop of 0.1 N HC1 brown-red stain; HC1 causes slow fading
Heavy Sr
Sr
Se
Si
iVa
6
Sn
W
A.
metals,
soluble PbbAieded.Li(+)
Cu
-
when
POa---(-), N(-), AU (brown ppt. soluble in excess reagent), C u ( - ) , V (very light blue color, does not interfere), Bi (yellow color), As(-), S b ( - ) , Cr (blue, green, or brown color. Very large amounts mask the test)
Only interfering element in this group ia Cr.
AS(+)
Arsenic may be removed by evaporating test drop in presence of 1 drop of concd. HCI.
Pb(-)
As(+),
PolL-- (whit; ppt.)
blue upon addition of SnCb), Mo (red stain on edqe of drop), F e (red stain: disappears upon addition of SnCIz), Se (red color in center oi spot) Pod---( -1 Sn(-), Cr(+) B; (yellow-brown color),'I(+)
Acid Group POa---(slight -), Sr (red stain; faded by HCl), Pb (red stain; turns purple upon addition of HC1). As(-), S b ( - ) , CrC-,, Fe (green-blue stain)
(Continued on p a g e s 874 and 676)
Sulfide separation removes As and Pb. Large amounts of T i reduce sensitivity. POI--- interferes, owine t o maskine effect of zinc phosphate ppt.
-
Test is
Cr Br I Sn and large amounts of $Or-'--'inte;fere. Confirm by 1 drop of soln , 1 drop of concd HgSOc, 1 drop of H A Red color.
Sr stain differentiated from Ba stain since it fades quickly ,upon addition of HC1 All other possible interferences are eliminated by pptn. as sulfides.
274
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 13, No. 4
TABLE I (Continued) Element
Procedure
Interferences Listed F e d (5, 4) Lange (7)
Bi
Spot plate 1. 1 drop of s o h . 2. 1 drop of thiourea 3. 1 drop of “01 Yellow color
Not listed
Cd
Spot plate 1. 1drop of diphenylcarbaride thiocyanate 2. 1 drop of soln. 3. 1 drop of sodium acetate 4. 1 drop of “4OH Violet-pink color Watch glass 1. 2 drops of soln. 2. 1 drop of (”4)ZS 3. Warm, filter Spot plate (black) . . 1. Filtrate A 2. 1 drop of fresh saturated soln. of dihydroxy tartaric osazone Yellow precipitate Filter paper 1. 1 drop of soln. 2. 1 drop of a-nitroso-%naphthol 3. Hold over NHdOH Brown stain
Only very large amounts of Hg, Pb, and Bi interfere
Ca
co
cu
AU
Fe
Pb
Mg
Mn
Casserole 1. 1 drop of s o h . 2. 1 drop of (NHdzHPOd 3. Acidify (concd. HzS04) 4. 1 drop of ZnSO4 5 . 1 drop of,ammonium mercuric thiocyanate Violet ppt. Filter paper 1. 1 drop of soln. 2. 1 drop of SnCIz 3. 1 drop of KCNS 4. Boi1,in water Purple stain Spot plate 1. 1 drop of soln. 2. 1 drop of KCNS 3. 1 drop of 0.1 N HCI Red color SDot d a t e -1. - 1 drop of soln. 2. 2 drops of K C N 3. 1 drop of NHdCl 4. 1 drop of dithirone 5 . Compare a t once with blank Pink color in CClr layer A. Watch glass 1. 2 drops of s o h . 2. 1 drop of (NHdrS 3. Warm and filter B. Spot plate (white) 1. 1 drop of s o h . A 2. 1 drop of K C N 3. 1 drop of Titan yellow 4. 1 drop of 5 N NaOH Red color Casserole 1. Portion of original sample 2. I to 4 drops of AgNOs
Interferences F m n d a
Acid Group (Con’t) Specific Pod---(-), Au (brown ppt., soluble in excess reagent), V (blue color), AS(-), Sb(-), Cr (masks), Se (red ppt,, masks) Specific within Pod--- (slow up reaction), Group I1 C u ( + ) , Ag(+), Au(+), H (+), V (blood red coTor), A s ( - ) , Sb(-) Cr(+), W+), Pd (purple color), B i ( + ) , N i ( + ) , Co(purp1e color)
Remarks Specific. All possible interferences appear in aqueous group.
411 interferences except Cu and Fe are eliminated by NazCOa-NazOs separation Fereduced t o ferrousstate does notinterfere. Cu does not interfere if crystal of K I is added to reagent prior to test.
Only alka,li and ammonium salts may be present
Alkaline earth metals
All interferences are removed except those due to Be, Sr, and Ba. Very large amounts of Mg may give false test.
Fe, U, Cu, P d
None listed
V and Cr appear in aqueous group. Zr
Fe, Cd, Co, Ni
Not listed
Au (brick-red ppt, masks), Cd ( owder-blul ppt.), Fe (re3 color), Co green ppt.) Ni (greenlue ppt.)
Cu, U, and Fe interferences may b; prevented by adding 1 drop of HsPO, and 1 drop K I to 1 drop of soln. on watch glass, stirring, then adding 2 drops of NatSoOa. Test on resulting soln. is specific. Gold is only interference if a control is run since colors due t o other elements do not mask nor resemble poaitive Cutest.
b
Not listed
Not listed
Pod-;-, organic hydroxyl compounds, Hg, NOz-
Not listed
P O & - - - ( - ) , Cu (slight yellow color), Au(+), Hg(-), Ag(-), A S ( - ) , Cr (masks), M o ( + ) . F ( - ) , Mn (masks)
Specific
S n + + ,Bi, TI
Sb(+), Bi(+)
Al, Zn, Sn, Cd, Ni. Co
Al, Ni, Co, Mn; Zn, Sn, NH4
Test is specific when NazCOrNazOz and (NHdzS separations are used.
C1, I , Br
Not listed
Test is specific since interference due t o halogens may be prevented by adding excess AgNO:.
when the element was actually present. Table I summarizes the analytical procedures used and the findings of the investigation.
Conclusions A systematic study of interferences occurring with selected drop reactions has been made. The investigation dealt with tests for 38 elements.
Stain given by W is distinguished from true test fof,.4u by fact that W stain fades in boiling water while Au stain does not. SazCOs --?ialO, separation removes interferences due t o Pod---, Hg, Ag, Cr, Mo, and F. As, oxalates, citrates may be removed prior to test by eva orating in presence of 1 drop conod. RCI and roasting. Specific if blank and control are run, since Sb gives off-color green-brown soln. Bi gives red color similar to that given by Pb.
Special attention is given t o the types of interferences encountered and the term “positive interferences” is applied to interferences giving false tests. Interferences which inhibit a true positive test are designated by the term “negative interference”. The data obtained in this investigation are tabulated and applied to a study of the two-group sodium peroxide-sodium carbonate system of analysis. The effect of this separation on the elimination of interferences is noted.
April 15, 1941
ANALYTICAL EDITION
275
TABLE I (Concluded) Element
Interferences Listed F e i d (3,4) Lange (7) Interferences Founds Acid Group (Con’l)
Procedure
M n (Con’t)
3. 4.
Remarks
1 drop of Hap04 Few grains of (“4)~-
820s
Hg
Xi
Ag
Sr
Ti
U
Zn
Zr
(I
b
5. Warm Pink color Spot plate 1 . 1 drop of soln. 2. 1 drou of sodium acetatk 3. 1 drop of dimethylaminobenzal rhodanine 4. Run blank Pink color A. Watch glass 1 . 1 drop of s o h . 2. 1 drop of HzOz 3. 1 drop of (NHdzCOa 4. 1 drop of “,OH B. Filter paper 1. Absorb soln. A on tilter paper. 2 . 1 drop of dimethylglyoxime Pink stain Spot plate 1. 1 drop of acetic acid 2. 1 drop of KsCrO4 3. 1 drop of test s o h . containing (NHdzCOa Red ppt. A. Watch glass 1 . 2 drops of s o h . 2 . 2 drops of (NHdzS B. Filter paper 1 . Filtrate from A 2 . 1 small drop of 0.1 N HC1 3. 1 drop of KzCrO4 4. 1 drop of sodium rhodizonate Brown stain Spot plate 1. 1 drop of soln. 2 . 1 drop of Hap04 3. 1 drop of HlOz Yellow color A. Watch glass 1. 1 drop of soln. 2. 4 drops of NazSzOs B. Filter paper 1. Filtrate from A absorbed on filter aper 2 . 1 f r o p of KhFe(CN)a 3. 1 drou of 0.1 N HCI Brown stain Casserole 1. 1 drop of s o h . 2 . 1 drop of (NH4)zHPOi 3. 2 drops of Hzs04 4 . 1 drop of CuSO4 5 . 1 drou of ammonium mercuric thiocyanate 6. Warm Violet ppt. Glass spot plate 1. 1 drop of soln. 2. 1 drop of alizarin 3. Warm 4. 1 drop of HCI Brown-pink color
c1, c u may be prevented by adding 1 drop of NazHPOI t o test drop.
M n ( - ) . F e ( + ) , Co(+)
Test is specific when preliminary treatment A IS carried out.
Pd Pt Co B e + + + ’ + cO’ Cu, Mn, Fe
F e + + , Co, P d
None given
Not listed
Ba, heavy metals
Ba
Ag (masks), Pb(S-1, A s ( - ) .
Test drop should have p H between 6 and 7. Barium interference is prevented by pptn. as BaCrO4. Other interferences are removed by sulfide pptn.
F. C1 Br I V Cr,’Fe, ‘AAet&e
Not liited
V(+) Cr (blue color). Cl(-). Mot+), F(-), B r ( - ) , I (masks)
All interfering substances appear in aqueous group, making test specific.
Specific
Not listed
Be (blue stain). V (yellow stain), Fe (green stain)
Other stains are so light that test may be considered specific.
Co, Fe, Ni
Not listed
Au (red ppt.), Cd (off-color blue ppt.) Fe (red color), Ni (green’ppt.), Co (blue PPtJ
Test is specific if blank and control are run.
F,
Not listed
P04---(-) Si(-) Sb ), W ( - ) , I&(-,, k(-J-
All interferences appear in group, making test specific.
+
SO&--, Pod---, Mp, W, organic hydroxyacids
hlnO4- may be reduced with 1 drop of thiourea t o MnOz.zHz0 and filtered off, making test specific.
Sb(-), Fe(-)
aqueous
Interferences were studied without prior separations. positive interference (false test). -, negative interference (suppression of test).
+,
Literature Cited (1) Arthur, Paul, and Smith, 0. M.,
(2) (3)
(4) (5)
(6)
“Semimicro Qualitative Analysis”, 1st ed., New York, McGraw-Hill Book Co., 1938. Engelder, C. J., Dunkelberger, T. H., and Shiller, W. J., “Semimicro Qualitative Analysis”, New York, John Wiley & Sons, 1936. Feigl, F., “Qualitative Analyse mit Hilfe von Tiipfelreaktionen”, 2nd ed., Leipzig, Akademische Verlagsgesellschaft, 1935. Feial, F.. “Spot Tests”, New York, Nordeman Publishing Co., 1637. Gutzeit, G., HeEv. Chim. A d a , 12, 713, 839 (1929). Heller, K., Mikrochemie, 8 , 33 (1930).
(7) Lange, “Handbook of Chemistry”, 2nd ed., Sandusky, Handbook Publishers, Inc., 1937. (8) Nieuwenburg, C. J. van, and Dulfer, G., “Short Manual of Systematic Qualitative Analysis by Means of Modern Drop Reactions”, 2nd ed., Amsterdam, D . B. Centen, 1935. (9) West, P. W., and Smith, Lothrop, J . Chem. Education, 17, 13945 (1940). (10) Winkley, J. H,, Yanowski, L, K., and H ~ w, A.,~ ~ ~i chemie, 21, 102-15 (1936). PRESENTED before the Division of Microchemistry a t the 99th Meeting of the American Chemical Society, Cincinnati, Ohio.
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~~
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