ANALYTICAL CHEMISTRY
754
Wash the ceramic bodies thoroughly with water, dry a t 105" C., cool, and weigh. The weight of the coating is equal to the loss in weight of the ceramics corrected for the loss in weight of a similar number of uncoated ceramic bodies carried through the same procedure. The boron in the solution is determined as follows. Add 3 drops of methyl red indicator and, while stirring, neutralize with the saturated sodium hydroxide added dropwise from a buret. Add only 1drop in excess. lMake the solution just barely acid with 1 to 10 sulfuric acid and add 2 drops in excess. Cover the beaker, bring to a boil, and boil gently for 5 minutes. Cool in ice water until the solution has reached room temperature. Set up the beaker for titration with pH electrodes. Adjust the pH with the 0,015AVsodium hydroxide to a value between 7.0 and 7.3. Add 3.0 grams of mannitol and titrate with 0.015N sodium hydroxide back to the same pH. The sodium hydroxide is standardized against the stock boric acid solution in exactly the same way. The sample titration is corrected for a blank which has been carried through the entire procedure. RESULTS
Table I, 11, and I11 give data obtained when boron was determined in known solutions, coatings of ceramic resistors, and in National Bureau of Standards borax, respectively. DISCUSSION
The above results indicate that boron can be determined in the coatings of boron-carbon resistors with a precision and accuracy within about 5% where the amount of boron titrated varies from 50 to 500 7 . No account was taken of possible interferences except that due
Table 111. Determination of Boron in NBS Borax Carried through Analytical Procedure Recovery, %
B, Titrated
Av. = 99.4; c
=
2.8
to carbonates. According to Feigl (1) telluric and germanic acids are activated by polyhydroxy compounds, but their presence is unlikely. Most cations likely to interfere are similarly not present in the coatings, though they may be introduced from the ceramic. Interferences arising from the latter are minimized by always running uncoated ceramic bodies through the procedure and correcting the sample titration for any blank titration. LITERATURE CITED
(1) Feigl, F., "Chemistry of Specific, Selective, and Sensitive Reactions," p. 360, New York, Academic Press, 1949. (2) Foote, F. J.,ANAL.CHEM.,4,39 (1932). (3) Grisdale, R. O., Pfister, A. C., and Rooshroeck, W. V., Bell System Tech. J . , 30, 271 (1951). (4) Hillebrand, W. F., and Lundell, G. E.
F.,"-ipplied Inorganic Analvsis." D. 612. New York. John Wilev & Sons. 1929. ( 5 ) Hollanier,'lLI:, and kiernan, W,', ANAL.C A ~ Y .17, , 602 (1945). (6) Wilcox, L. V., Ibid., 2, 358 (1932). RECEIVED for review October 27, 1953.
Accepted January IS. 1954.
Benzilic Acid as a Reagent in Gravimetric Determination of Zirconium JOSEPH J. KLINGENBERG, PEPPINO N. VLANNES', and MELVIN G. MENDEL2 Xavier University, Cincinnati, O h i o
D
URING the investigation of the zirconium-precipitating
action of a number of glycolic acid derivatives by Oesper and Klingenberg (6) benzilic acid was found to give a very voluminous precipitate. Venkataramaniah and Rao (6) investigated this reaction further and found that quantitative precipitation occurs in solutions up to 0.225N in hydrochloric acid solution. The following work, carried out independently, parallels the results obtained by Venkataramaniah and Rao, but also studies the reaction under a wider range of conditions with thk resultant extension of the quantitative precipitation beyond the 0.225N hydrochloric acid range. (Contrary to the statement of Venkataramaniah and Rao, benzilic acid was not "totally rejected" as a zirconium reagent by Oesper and Klingenberg. The study of benzilic acid was delayed in favor of the more promising halomandelate reagents.)
tated by the addition of ammonium hydroxide. The gelatinous rnws is washed by reverse filtration until aliquots of the wash solution give negative tests for sulfate ion. The washed zirconium hydroxide is dissolved by the addition of hydrochloric acid, heating if necessary. White, tetragonal crystals of zircony1 chloride octahydrate are obtained by evaporation of the solution. Zirconyl chloride solution. Zirconyl chloride octahydrate is dissolved in distilled water containing 250 ml. of 12N hydrochloric acid per liter of solution. EXPERIMENT4L
Quantitative Action of Benzilic Acid. After considerable experimentation the following procedure was developed for the determination of zirconium. To a solution containing 0.0010 to 0.0600 gram of dissolved zirconium in a 250-ml. beaker are added 15 ml. of 12N hydro-
REAGENTS
Benzilic acid. Commercial benzilic acid is purified by recrystallization from hot water containing a little hydrochloric acid. By keeping the temperature below 95" C. the main contaminant, benzil, remains as a solid and can be removed from the dissolved benzilic acid by filtration. Zirconium sulfate solution. Commercial zirconium sulfate tetrahydrate is dissolved in distilled water containing 333 ml. of 12N hydrochloric acid per liter of solution. Zirconyl chloride octahydrate. Zirconium sulfate tetrahydrate is dissolved in water and zirconium hydroxide is precipi1 Present Address, Eastern Experimental Station, Bureau of Mines, College Park, Md. 2 Present Address, National Lead Co. of Ohio, Cincinnati, Ohio.
Table I.
iinalysis of Zirconium Solutions by Various Methods Reference t o Procedure
Zr(S0i)x Solution, Gram ZrOz/hll.a
ZrOCla Solution A, Gram ZrOt/hLa
ZrOClr Solution B, Gram ZrOz/Ml.'
...
0.0089 0,0089
0.0278 0.0278 0.0279
0.0090
0.0280 0.0278
Method Benzilate .. 0.0104 p-Bromomandelate (6) p-Chloromandelate (6) Cupferrate (3) O.'Olb4 Hydroxide (3) 0,0104 Mandelate (6) 0.0104 Phosphate (3) 0.0104 a Based on average of nine analyses.
...
0.0089 0.0089
0.0279
...
V O L U M E 26, NO. 4, A P R I L 1 9 5 4
755
manganese, carbon. iron, chromium, niokel, molybdenum, niobium, tungsten, cobalt, and zirconium were analyeed by the procedure doveloped by Klingenberg and Papucci ( 4 ) except that benzilic acid was used as the reagent. The results are g 4 - m in Tahlo T T T
bm0"nr)
gram
D'erenz.
0, oecerminstions
I0ll"il.
gram
Zralll
k. Preoinitation in Low leid Concentr;" 0.25
0.0089
0.50
0.0089
0.50 0.43 0.65
0.0089 0.0089 o.oo89
0.50
B.
Figure 1.
o.oos9
0.0088 0.0086 0.0088 0.0178 0.0084 0.0146
PreeiDitation in 10% Hsdrochiorio ~
O L U
Volume of Precipitate Produced with Zirconium by Various Reagents
chloric acid and water to give a total volume of 50 ml. This is heated to boiling and 100 ml. of a hot 2% solution of benzilic acid is added. (Solid benzilic acid may also he added to the solution diluted to 150 ml. with distilled water.) A milky precipitate appears immediately. This is digested a t 95' C. for approximately 10 minutes, whereupon the precipitate coagulates into flocks, then becomes more granular and collects into a coherent mass towards the center of the beaker. The preci itate is filtered while hot on a No. 40 Whatmrtn filter paper ! n a washed five or six times with hot water. (Gooeh or Selas crucibles may also be used.) The paper and contents are dried charred, and ignited in a muffle furnace a t 1000' C. using parceldin or platinum crucibles. The ignited material is then cooled and weighed. Table I compares the results obtained with solutions of zirconium sulfate and zirconyl chloride using benzilic wid and other reagents. Weighting Effect of Benzilic Acid. A comparison of the amount of precipitate obtained from equivalent amounts of airconium when treated with various reagents is shown in Figure 1. The methods of ureciuitation were the same as those used to obtain the data i i Table I. Effect of Acidity and Foreian Ions. In studying the effect of acidity on the precipitation the results agreed approximately with those reported by Venkataramaniah and Rao (5)-i.e., using 1% bemilic acid, the precipitation became incomplete as the acidity wag rai.ised heyand 0.23N. However, i t was observed that this effect could be counteracted by increasing the concentration of the bemilie acid. This is strikingly illustrated by the photographs in Figures 2 and 3, and the analytical results summarized in Figure 4. This data wa8 used in selecting the conditions of precipitation a8 outlined above. The value of using a higher acidity lies in the fact that precipitation of foreign ions is noticeably lessened. This is illustrated by the data in Tahle 11. Part A represents the results obtained by the method previously described using 2% benzilic acid solutions, but with no added hydrachloric acid. Part B represents results obtained using 2% bemilie acid solutions with 15 ml. of hydrochloric acid per 150 ml. of solution. In Figure 2. this case tin and iron were found to interfere no longer. Application to Steel Samples. Five steel samples containing silica, sulfur, phosphorus,
Table 111. D e t e r m i n a t i o n of Zirconium in Steel Samples samlde
\lethod Mandelate p-Bromomandelate P-Chloromandeiste Bonziizte
NO
2036
Mandelate p-Brornainandelate Benrilste
2161
Ifandelate
2058
wt ZrO2, GI*"> 0.0018 0.0018 0.0018 0.0018
Zr, % .. 0.07 0.07 0.07 0.07
No. of Detns. 6 6 6 6
0.0030 0.0030
0.07 0.07
6 6
0.07
G
0.06 0 06 0.06
6 6 6
0.0044
0.11 0.11 0.11
6 6 6
o.0041
0.10
0.0041
0.10 0.10
0.0030 0.0011
p-BP3mO"la"dd8fe
0.0017
Benziiate
0.0016
Mandelate p-Bromomandelate Bcnziiate
222;
Mandelu*te p-Chloroinandelste Benrilate
2166
0.0042 0.0042
0.0041
6 ,
6 6
Inhibition of Precipitation of Zirconium w i t h 1% Benzilio Acid by Inoreasing Acidity
preceding work on the direct weighing of aireonium benzilate an investigation of the composition of the precipitate was undertaken. Zirconium benzilate was prepared as described above, collected on Selas crucibles using suction, and washed as follows: ( a ) with hot water, (6) with 20% ethyl alcohol, and (c) with 2N hydrochloric acid solution. The precipitates s e r e then analyaed for carbon, hydrogen, zirconium, and oxygen (by difference). The results are given in Table V. Although no definite conolusions can be reaohed from the dsts, the empirical formulas approximate the coordination types postulated by Blumenthal ( 1 ) and Feigl (8). The basic salt type of compound formulated
< $ ~
Negoti*r
-
-
2
-
0
E
s
'L~O-
Determination of Zirconium as Zirconium Benzilate
zireoninm Oxide Taken, Gram
Zirconism Benzilate. Gram
ZirW"i"m Oxide Cslod. from Ziroonium Benrilate,n Gram
Zirconium Oxide Obtained by Ignition, Gram
; 125-
T I *r ,* , , lr oo r, e I , r c o " i " n
P.cciPilalln* CD"dili0"l
I
e " I w N
C6ndttiOnl
L.ICEI.d
POIIIIYD
.-
Table IV.
Pcb(.iPIIoII.q
../
f 1.75
For z,rrsn,urn i n F , , l r o , .
\
f
e
TIS!
O
F/,l,l, I
04
0.8
12
1.6
2.0
2"
