ANALYTICAL CHEMISTRY
512 free thujaplicins. Therefore, in preparing standards and ralibration plots. all solutions were freshly prepsred and carefully protected from light during storage. LITERATURE CITED
(1) Anderson. A. B.. Gripenberg. J.. Acta Chem. Scand. 2, 644. (1948). (2) Barton, G. M.. Gardner, J. A. F., Pulp & P a p e r .Vag. Can. 55, 10, 132 (1959). (3) Cook. J. VI., Gibb. A. R., Raphael, R. A,. Somerdle. A. R.. 3. Chem. Soc. 1951. 107.
(4) Dutton. G.G. S.. Gardner. J. A. F.. unpublished results. (5) Erdtman. H.,Gripenberg. J . , Acto Chem. Sand. 2, 625 (1948). (6) Erdtman, H.. Gripenberg. J.. Nature 161,719 (1948). (7) Gripenberg, J . , Acta Chem. S c a d . 3,782 (1949). (8) hlaelean, H..Gerdner. J. A. F.. unpublished data. (9) Nozoe. T.. Bull. Chem. SOC.Japan 11,295 (1936). (10) Nosoe, T.. Science Rep&. T6hoku Unio.. FGst SeriCa 34, 199-236 (1950). (11) Rennerfelt, E.,PhusiOl. Plantarum 1, 245 (1948). (12) Roff,J. W., Atkinson. J. AI.. Can. J . Botany 32, 308 (1954). R e c ~ i v ~for o review September 2. 1855.
Accepted January 14, 1956
Semimicrodetermination of Fluorine in Organic Fluoro Compounds CHAlM EGER and ASHER YARDEN Scientific Department, Israel Ministry of Defence, TeI-Aviv,
A s i m p l e s e m i m i e m m e t h o d for the d e t e r m i n a t i o n of fluorine i n organic fluom compounds irr described. T h e sample is ignited i n a modified Parr s o d i u m pemxide bomb and the solution of the m e l t is percolated t h r o u g h an acidic c a t i o n exchanger. The neutralized percolate is t i t r a t e d w i t h t h o r i u m n i t r a t e , using s o d i u m alizarin sulfonateas indicator. In fluom c o m p o u n d s which also c o n t a i n chlorine or b m m i n e , the various halogens can he determined simultaneously.
A
NUMBER of methods have been proposed far the transformatron of organic fluorine into titratable fluoride ions, including: (a)oxidation with gaseous oxygen (7, 14. 65, SS, 85) or sodium peroxide in a nickel bomb (19, 24, 87), with addition of benzoic acid or sucrose as combustion aids and, sometimps, of potassium nitrate or perchlorate as accelerator; ( b ) reduction by the hydrogen flame (11, 86) or alkali metal (16, 17, 20, 28, 80, S4); and (c) fusion with calcium oxide ( 1 , $1, 29) or sodium carbonate (9). Another method involves the reaction of hydrogen fluoride, formed in the destruction of the organic fluoro compound, with silica (10, 12, 18). Occasionally the organically bound fluorine is liberated hydrolytically by aqueous ammonia solution ($6,SO). The present investigation, which has already been briefly noted (15),has shown that the combustion with sodium peroxide is the most convenient and reliable method; however, the 2.5-ml. Parr mierohomb which is ignited by flame did not give reliahle results, and the 22-ml. electric ignition bomb bad too large a capacity. An electrical ignition bomb of 8-ml. capacity was, therefore, constructed and used successfully. The fluoride ion formed in the combustion is contaminated with a relatively large quantity of sodium hydroxide and other sodium salts which interfere with the subsequent fluoride determination. Gravimetric determinations [calcium fluoride or lead chlorofluoride (3711 failed a t the fluoride concentrations studied because precipitation was not quantitative. The usual distillation method (881, even after a number of improvements, tended to give low results, especially when the fluorine content was small. It therefore proved necessary to eliminate the sodium ion from the fluoride solution. This was achieved by means of the acid form of a cation exchanger. In the percolate, which contained, in addition to hydrofluoric acid, small quantities of carbonic and hydrochloric acids (when potassium perchlorate was used as combustion accelerator), the fluoride ion can he determined by titration with thorium nitrate, using sndium alizarin sulfonate 88 indicator. This method (8) has been improved by mme minor modifications.
nzagenrs ana aorunons. ur;tnuaru wmum nuonae solution
(0.1mg. of fluoride ion per ml.) was prepared by dissolving 0.221 gram of s3diurn fluoride (Baker analyzed reagent recrystallized once from distilled water and dried) in distilled water, adding 1 ml. of O.l.V sJdium hydroxide solution, and making up to 1 liter. rnL-~~:..-~ olution. An 84' solution dissolving 5 itrate (tetrad y s e d reaof distilled qe w a s obiim fluoride -:/~~-1~
~i~~~ 1. pemride bomb, assembled
100 &I,of distilled water (a* proximately 1.W). To this sohtion a ldl acetic acid (AnalnK) sol&ion wa8 added to pH 3.55 on a. Beekman Model G DH motar
Ethyl alcohol, redistilled on&.' Sucrose, AnalaR. Potassium perchlorate, Parr Co. Ion exchanger. I n the present investigation, Amberlite IR112 (Rohm & Ham, Phildelphia) wa8 used. Rohm & Haas have discontinued the production of this specific ion exchange resin, and have substituted for it Amberlite EX-100. Any acidic ion exchange resin can be used in the method described. Anoaratus. An Rml. semimicro electric ienition bomb was constructed (Figures 1, 2, and 3 ) . ~The cups were made of stainless ateel, the ot,her parts of nickelelectroplated brass. A length of 3.5 cm. of fuse wire (Parr Co.) was used, and a resistance of 1 ohm was incorporated into the ignition circuit. The water bath xnd~ignitionunit used were those of the original Parr instrument ~~~~
($8).
~
~
Procedure. PREPARITION OF CALIBRATIOX CURVE. With an automatic microburet of 5-ml. capacity, 1, 2, 3, 4, and 5 ml. of the standard sodium fluoride solution were measured into five Erlenmeyer flasks of 50-ml. captpacity. Water was added to make a total of 10 ml. of solution. The reagents were then added to each flask in the following order: 0.2ml. of indicator solution; hydrochloric acid (approximately 0.1N) drop by drop. until the color turned from red to yellow; 10 ml. of ethyl alcohol; and
V O L U M E 28, NO. 4, A P R l L 1 9 5 6
513
finally, 2 ml. of the huger solution. The solution was titrated with the thorium nitrate solution. using an automatic 5-ml. niirroburet. The end point was the change of color from orange to red. Each determination wa8 repented five timee (Tahle I), and the mean values were plgtted. The calibration curve wa6 checked for each new solution of thorium nitrate and, if necessary, rorrected.
prevent any creeping of the percolated solution. The tube T\'BLI then filled with the pretreated ion exchange r a i n a6 uniiormly a8 possible to prevent channeling, leaving a free space of about 5-em. length a t the bop of the column. Regeneration. After each analysis the resin was regenerated by passing 1 liter of B 5% sulfuric acid solution through the rolumn a t a rate of approximately 2 ml. per minute. This was followed with distilkd water until no sulfate ions could he det r e t d in the prrcolnte. The regeneration and washing of the column were carried nut with the help of a simple device shown in Figure 4. A hottle of npproximatrly 1-liter capacity was filled
umn. The gla& tuhe p r a t h l h g from the stopper entered the empty space a t thc upper part of the column. This device eliminates any overflow and work8 unntbended. ANALYTICAL XIETHOD. A sample of 20 to 60 mg. of the dried and powdered organic flnoro compound is weighed into the stainless stw1 cup of the romhwtion homh. The w i g h t of the sample is chosen so that the final concentration of fluoride ion is 0.1 to 0.3 ~" - ~I n - .._I -
