SEPTEMBER 1947
651
by the general method, as n ell as optional procedures for samplcs of special composition, are given. A simple test for inhibition and sensitivity eliminates any chance of false conclusions. ACKNOWLEDGMEhT
This study was conducted under the general direction of S. R. Zimmerley, chief, Salt Lake City Division, Xetallurgical Branch, Bureau of Mines, and E. V. Potter, in charge of the A n a l y t i d and Testing Section. T h e authors wish t o acknowledge the assistance of their associates who have helped in carrying out these experiments. They are particularly indebted t o S. F. Ravitz for assistance in preparing the manuscript and offering suggestions, and to HoLYard Tribe for preparing the photographs.
LITEHATUHE CITED
(1) Hoffman, J. I., and Lundell, G. E. F., Research .\-ntl. Biir. Standards, 22, 465-70 (1939). (2) Nichols, E. G., Howes, H. L., Merritt, E.. Wilber, D. T., and Wick. F. G., Carnegie Inst. Wash., Pub. 298, 1 (19191. IXD! EXG.CHEIW., . ~ N A L .ED., 17, fib4 (1945). (3) Northrup, M. a,, (4) Pringsheim, P., and Vogel, H., Physica, 7, 223-40 (1940). (5) Sill, C. K., and Peterson, H. E., U. S. Bur. \line?:. Irifgrmation Circ. 7337 (August 1945). (6) Smith, F. W., IXD. EXG.CHEM.,.ris.i~.. ED.. 10, 360 (1938). (7) Tomaschek, R., and Deutschbein, O., Ann. P h y s i k . , 16, 943 (1933): 28, 673 (1937); 29, 311 (1937). (8) Zaidel, A , , Larienov, J., and Philipo~,d. N..J . Gen. C'hem. (U.S.S.R.), 8, 943-8 (1938). PCBLISHED t)y permission of tlle Director, Bureau of LIiIit-, 1..5 . D e p a r t ineiit of tlie Iiitrrior.
Determination of Phosphorus in Phosphate Rock Separation from Cations by Ion-Exchange Resin KENNETH HELRICH AND WILLI.431 RIEnlAS 111 School of Chemistry, Rutgers Cnicersity, ,Yew Brunswick, S. J .
I n determining phosphorus in phosphate rock, the solution in hydrochloric acid is evaporated to remove most of the fluoride ion and dehydrate the silica. The residue is treated with dilute hydrochloric acid, and this solution is passed through a cation-exchange resin previously saturated with hydrogen ion. The effluent, which contains only hydrochlo-
A
L T H O U G H ion-exchange resins have been known for some time, there have been few applications to the problems of analytical chemistry ( 2 , 3-7). B y making use of an ion-exchange column in the separation, the proposed method for the determination of phosphorus can be run much more quickly a i d requires a great deal less skill than the standard method of Hoffniaii and Lundell ( 2 ) . REAGENTS
ric and phosphoric acids, is adjusted to a pH of 4.63 to convert the acids into sodium chloride and sodium dihydrogen phosphate. Titration with sodium hydroxide to a pH 8.98 converts the priniary phosphate to the secondary salt and gives a rapid and accurate determination of phosphorus. A n d y sis of a sample in duplicate requires less than 4 hours.
Regenerate the exchanger bj- pouring through i t 330 mi. of 1 N hydrochloric acid follon.ed by 300 ml. of diotillcd viv-!er. Keep the solution level approximately 2 em. above the h t d k v e l by passing all solutions into the column through a separri tu:y funnel fitted in the top of the columii by means of a tir-o-hole rubber stopper. T h e rate oi flt~w through the resin should be sac,h r h t ~ ! : eentire operation requirvs 2~~ niiiiutes. The column should Le l,:tr*kn-ashed and rogerierated just tjefure t,:i%'ll determination.
Sodium hydroxide, 0.1 * 0.02 -V,carbonate-free, standardized. Sodium hydroxide, 18 S,stored in a paraffin-lined bottle. Hydrochloric acid, approximately 0.1 -Y,1.0 .Y.and 6 S. Methyl red indicator, 0.1 %. Phenolphthalein indicator, 1yo. Buffer, p H = 4.63. 17 ml. of 1.3 Ill sodium acetate, 25 nil. of 1.0 M acetic acid, 360 ml. of water, and 3 drops of methyl red. Buffer, p H = 8.98. 130 ml. of 0.1 31 borax, 40 ml. of 0.1 .lI hydrochloric acid, 230 ml. of water. 3 drops of niethvl red, and 1 drop of phenolphthalein.
PROCEDCRE
\\-eigh 450 to 550 mg. of sample into a 150-ml. beaker. :tc!cl i.5 nd. of 12 hydrochloric acici, (> a x a t c h glass, and t~,>i! K 30 minutes. Evaporate t u dryness on a steam bath Si:d tiulie there for 1 hour. Add 2 nil. of 6 .V hydrochloric acid and 98 ml. of wd:er. \Thile the solution is beiiig evaporated. baclwash, regellcrate, and n-ash the column as directe,l a h v t . . Then pass the solution t!iroug!i at the .same rate and in the u w manner as in t,he regcneration, wl!t.:>rii:g the filtrate in a 1-liter c a s ~ e r i ~ l e \Vash . with 300 ml. of water at tlie s q e rate and collect the wtsii \\-:iter 111 the same casserole. The total t h e for passage of sample and n-ash water should be appr,~ximntely 10 minutes. .Add 3 drops of O.ic; illethyl rcd and then add 16 .V +cdiuni hydroxide until the si~luti~>Il1s yelloxY.. Immediately, add 1.0 .V A\-
PREPARATlOh OF COLUMN
The ion-exchange column illustrated in Figure 1 may be obtained from the Ace Glass Company on special order. The specifications should be for S o . 85678 filter tubes, porosity A, 400 mm. long, m-ith stopcocks a t the bottom. T o prepare the column, suspend in water sufficient Aniberlite IR-100-H A.G. (Resinous Products and Chemical Company, Philadelphia, P a . ) to give a bed volume of approximately 170 ml. Pour this into the glass tube. Backwash the exchanger with t a p water by connecting a rubber tube from the t a p to the bottom of the column and another tube, fitted in a rubber stopper, t o the top of t h e column t o carry off the water. Pass the water through' slowly, so t h a t none of the resin is washed out through the upper tube.
-
Figure 1. IonExchange Column A. B. C.
Water Amberlite Sintered glasu
V O L U M E 19, NO. 9
652 Table 1. Experimental Results Sar.iyle
P?O&
Bureau
Value
/-ingelements when pulverized in the customary mannrr and by a variant procedurc. hIORTAR
T h e samples xvere crushed in a mortar of the common Plat,tner type, KO. 17360 B of the Central Scientific Company. T h e inner cylindrical portion vas 3.5 em. in diameter and 1.6 cm.
high. The diameter of the pestle as 2.5 cm. The collar, which fitted both the mortar and pestle very snugly, had a height of 3.5 em. The mortar had been used prior to the present experiments and the face of the pestle, as n-ell as the floor of the mortar, was appreciably roughened by abrasion. The sides of the collar also shoved signs of abrasion. SAMPLES
Because of its purity and hardness, quartz is the logical test substance, b u t a sample of microcline was also crushed t o learn the effect of loner hardness and different crushing characteristics. The samples n-ere prepared as follows:
Quartz IA. Pieces of clear quartz crystal, up to approximatcly 1 cm. in diameter but mostly smaller, were tapped 20 times in the mortar with moderately heavy hammer blows. The crushed material was then sifted through a screen which consisted of a sheet of rag paper perforated with numerous holes 0.7 mm. in diameter. The material remaining on the screen was returned t o the mortar, tapped as before, and sifted, and new fragments of quartz were added when but little of the previous charge remained. After 200 tappings, 95% of the total sample had passed through the sieve. The remaining fraction was combined with the sifted portion and the whole mixed (weight 9 'grams). The powder thus obtained was not pure white, and small slivers of steel could be seen in it here and there under low magnifiration.
