1067
V O L U M E 24, NO. 6, J U N E 1 9 5 2
composition is hrlon approximately 80% glycol, and the refractive i n t i ~ x(;:++ashould be useful in drterniiriing the glycol cont c s n t to u i t h i i i I0.1 \\-eight yoover the entire composition range. P X P 'water IJr, 1
DG 2 DG 3 DG 4 DG 5 DG 6 DG 7 DG 8
DG Y
9 97 19.79
'I'ali!e
29 70
I )it,tliylne Gl,.col.
39 46
1 06303 1 07.m
49 73
69 78 69, 67 79 74 89 8 9
I0
(1
00000
mnni
Purified dic thl-ltne gl)-col
__ REFRACTIVE I S D E X hIEASUREMEh~TS
Refractive index values were measured by means of a Carl h i s s dipping refractometer and a constant temperature bath kept at 25" i 0.1" C. 9 sodium lanip served as the light source. Using this instrument, the values of refractive index are believed to be correct t o within j=O.OOOl. -1s a result of the relatively constant, rate of change of refractive index with composition as shown in Figure 2, the precision mentioned corresponds t o a composition difference of about 5 0.1 weight R over the entire composition range. In summary, the densit'y data presented may be used in detertnining the glycol content within 10.03 weight % when the
I I.
Smoothed \'slues
Refractive Index,
Weight
ns5
Absolute Density, G./RZl. a t 35.00' C.
0
1.3325 1.3436 1.3550 1 3670 1 3788 1.3912 1.4032 1.4150 1,4261 1,4364 1,4461
0.99406 (3) 1.00733 1.02116 1.03x 1.04964 1.06340 1.07695 1.08695 1.09569 1.10189 1.10555
10 20 30 40 50 60 70 80 90 100
00 00 00 00 00 00 00 00 00 00
LITERATURE CITED
(1) Carbide and Carbon Chemicals Corp., New York, "Glycols," 1947.
( 2 ) RIacBeth, G., and Thompson, A. R., ANAL. CHEM., 23, 618
(1951). (3) Reilly, J., and Rae, W. N., "Physico-Chemical Methods," 3rd ed., Vol. I, X e w York, D. Van Nostrand Co., 1939. (4) Rinkenbach, W ,H., Ind. Eng. Chem., 19, 4 i 4 (1927). RECEIYED for review December 8, 1951.
Accepted February 10, 1962.
Determination of Phosphate by lor: Exchange ALEXANDER J . GOUDIE' AND WM. RIERIAN I11 School of Chemistry, Rutgers Cniversity, New Brunswick, .V. .I. RE-EX4SIIN.4TIOX of the ion-exchange procedure for the A ! determination of phosphate ( 3 ) seemed desirable for three
reasons. 1. Since this method was first proposed ( S ) , monofunctional high-capacity resins of the strong-acid type ( 1 ) have become arailable comriiercially in a wide variety of particle sizes. The uje of theye resins permits a more efficient separation of phosphoric acid from interfering cations. 2 . Dijksnian believed that the presence of carbonate in t'he titration was a serious source of error in this determination, and recommended ( 2 ) elaborate precautions for its exclusion. 3. Shortly after the ion-exchange method x-as recommended (3),it \vas observed in this laboratory that positive errors were incurred when the ion-exchange column was subjected to repeated use. Thib error was much worse with a sulfonated polystyrene resin than with Amberlite IR-100. Investigation revealed that the cause of the error vias failure of the regenerat'ion procedure t80remove the ferric ion completely from the column. >lore and more ferric ion was retained by the resin with repeated use unt,il a sufficient quantity was accumulated so t h a t an apprecisble amount of ferric ion appeared in the eluate with the phosphoTic acid. Then part of the phosphate 1%-asconverted t o the tertiary state a t the second end point (pH = 8.98). This error amounted to O.i% phosphorus pentoxide after ten determinations had been performed with one column according t o the directions given below, except that only 100 ml. of 4 111 hydrochloric acid \!-ere used in each regeneration. +4sthe removal of iron by hydrochloric acid proved t o be impracticable, diaminonium citrate x a s used as a coniplesing agent in the regeneration. PREPARATION OF COLUMN
Stir 35 grziiia of Dovex-50 (100 to 200 mesh, purchased from bIicrocheniica1 Specialties Co., 1834 University Bve., Berkeley 3, Calif.) with 200 ml. of water in a 250-ml. beaker. Let the coarse particles settle for 1 minute and decant the suspended fine particles into the sink. Repeat this procedure several times until a clear supernatant liquid is obtained. Place a bed of 15 ml. of the resin in a 30-ml. filter tube provided TTith a porous sintered-glass 1
Presenr address, Central Research Laboratory, Allied Chemical and Dye
Corp., blorristown, X.
J.
disk (Bllihn filter tube KO.8571, porosity 8,from Ace Glass Co. is very convenient). Attach a short piece of rubber tube with a pinch clamp to the bottom of the filter tube. Regenerate the column before each use as follows. Pass through the column 125 ml. of 1 144 diammonium citrate, then 250 ml. of 6 31 hydrochloric acid. Add a little water t o the column, stir the resin, and finally wash it with 250 ml. of water. Open the pinch clamp wide for the flow, but take care that the resin is always covered with liquid. STANDARDIZATION OF 0.1 N SODIUM HYDROXIDE
Prepare 0.1 A- sodium hydroxide by diluting the 18 N solution with carbonate-free water. To standardize the solution, weigh about 350 nig. of pure potassium dihydrogen phosphate, previously dried a t 110" for l hour. Dissolve this in 150 ml. of water and add 2 ml. of 6 144 hydrochloric acid and 3 drops of 0.003 -11methyl orange. ildd 18 11.17 sodium hydroside dropwise until the indicator turns yellow; then add 1 M hydrochloric acid dropwise until the indicator turns red. Titrate n-ith the sodium hydroxide solution, using a p H meter. In the vicinity of p H 4.6 and 9.1 (corresponding t o the formation of primary and secondary phosphates, respectively), add the solution in uniform increments of 0.20 ml. Take as the end points those buret readings for which A2pH is zero. DETER3llS.4TlOX O F PHOSPHORUS Iii PHOSPHATE ROCK
Treat a sample of 0.4 to 0.45 gram in a covered 150-iii1. beaker rrith 15 nil. of 12 -11hj-drochloric acid and boil gently for 30 minutes. Then evaporate the solution to dryness on a hot plate, and bake in an oven a t 110" for 1 hour. Add 2 ml. of 6 M hydrochloric acid and 20 nil. of n-ater in this order. When t,he sample is redissolved, filter the solution, and wash n-ith rrater until the total filtrate is 65 nil. It is convenient to regenerate the colunin during the foregoing steps. Transfer the solution to a dropping funnel attached to the ionexchange column. Pass the solution through the column with the pinch clamp TT-ide open. The rate will be about 5 nil. per minute. Wash the beaker, dropping funnel, and column with water until a total of 150 ml. of eluate is collected. Treat this with 18 A4 sodium hydroxide and 1 144 hydrochloric acid, and titrate as in the st,andardixation.
ANALYTICAL CHEMISTRY
1068 RESULTS
A comparison of results obtained by this method with those certified by the National Bureau of Standards is given in Table I. Each sample was analyzed three or four times.
Table I. Analysis of Standard Samples Sample No. 120 56B
Values Found Mean % Mean deviation,
Bureau Value, % 35.33 31.55
PloS
%
35.38 31.53
10.02 10.03
hydrogen phthalate with precautions to exclude carbon dioxide (use of recently boiled and cooled water and passage of a stream of purified air through the solution during the titration), the mean value was 0.08333 N . Standardization by the recommended procedure, except that carbon dioxide was excluded, yielded a mean value of 0.08355 N. These data indicate the importance of taking precautions to avoid the carbonate error. The precautions may be either t o standardize and titrate the unknown under identical conditions, as recommended in this article, or to exclude carbon dioxide in both standardization and analysis, as recommended by Dijksman (8). The former procedure is more convenient. ACKNOWLEDGMENT
DISCUSSION
Effect of Carbonates. By standardizing the sodium hydroxide solution against a phosphate with titration conditions identical to those in the analysis, the effect of sodium carbonate in the sodium hydroxide and of carbonic acid in the water is eliminated. The results given in Table I were obtained with a solution of sodium hydroxide that was 0.08302 N by the recommended standardization. When it was standardized against potassium
The authors are indebted to Dragomir Dutina for same preliminary work on this problem. LITERATURE CITED
(1) Bauman, W. C.,and Eichhorn, J., J . Am. Chem. Soc., 69, 2830 (1947).
(2) Dijksman, J. C. W., Rec. trav. chim., 68, 57 (1949). (3) Helrich, K., and Rieman, W., Anal. Chem., 19, 651 (1947).
RECEIVED for review August 7, 1951. Accepted January 2, 1952.
Determination of Soap, Acid, and Alkali in Synthetic latices S.H. MARON, I. N. ULEVITCH, AND &I. E. ELDER Department of Chemistry and Chemical Engineering, Case Institute of Technology, Cleveland, Ohio N A recent paper it was shown that conductometric titraIwater tions, when run in a 1 to 1 mixture of isopropyl alcohol and as solvent, can be applied satisfactorily to fatty and rosin
shown below t h a t the free alkali content of latices, like that of soaps, cannot be determined reliably by direct titration with acid.
acids, soaps, and acid-soap mixtures. The present paper describes an extension of these procedures to the determination of the same constituents in synthetic rubber latices.
Direct Titration of Fatty and Rosin Acids with Base. Because the free fatty or rwin acid contents of normal GR-S latices are usually low, approximately 50-gram samples of latex were taken for acid determinations. These samples were diluted with 200 ml. of distilled water, followed by 200 ml. of isopropyl alcohol, and then titrated conductometrically with 0.05 N sodium hydroxide.
(1)
Table I. Direct Titration of Fatty and Rosin Soaps with Acid i n GR-S Latices Latex Type I1 No. 210 (fatty acid) Type 11’ No. 225 (fatty acid) Type IIi, No. FS-12 (rosin acid)
No. of Detns. 4 3
4
Me. HCI/Gram Sample 0.0468 fO.0001 0.0452 1 0 . 0 0 0 2 0.0834 i 0.0001
EXPERIMEKTAL DETAILS
The apparatus and reagents employed have been described (1). The essential difference in procedure involved dilution of the latex samples with 200 ml. of distilled water, followed by addition of 200 ml. of 99% isopropyl alcohol. It is imperative that the water be added first, for otherwise the alcohol will cause lation of the latex. e latices were in all instances commercial products, Type I1 latex containing fatty acid soaps, and Type I11 rosin acid soaps. Direct Titration of Fatty and Rosin Soaps with Acid. To determine the soap content of a latex, 10- to 16-gram samples were weighed into a 600-ml. beaker and diluted with 200 ml. of distilled water. Next a mechanical stirrer was introduced, and, while the sample was being agitated, 200 ml. of isopropyl alcohol were added. These samples were titrated conductometrically with 0.10 N hydrochloric acid (1). Typical conductance curves obtained from such titrations are shown in Figure 1. As sharp breaks occur a t the end points, there is no difficulty in ascertaining the equivalence points. The results obtained for several latices and given in Table I show the concordance to be within 0.5%. The fact that the curves in Figure 1 do not show an initial decrease in conductance followed by an upswing is an indication that no free alkali was present in the samples tested. Although the presence of free alkali can be detected in this manner, it is
Typical conductance curves obtained with Type I1 and I11 latices are shown in Figure 2. As observed ( 1 ) with soap solutions containing free acid, the titration curve8 consist of three straight lines intersecting at two points. Study of latices with known free acid contents has again established that the end point sought is the first of these discontinuities-Le., the one marked by the arrows in Figure 2.
6ol
50
,
20
40
I
60 VOLUME
I
80
I
I00
I20
140
HCI ADDED-ML.
Figure 1. Titration of Fatty or Rosin Soaps i n Latex with Acid Typical conductance plotm
