phate ion is present in a concentration greater than 1 p.p.m., it must be removed by distillation. Interference due to iron is shown in Figure 5 . This interference is undoubtedly caused by the formation of a Fe(II1)-phenylfluorone comples. At a concentration above 0.5 p.p.ni., iron produces a deep blue as opposed to thti deeu rose of the thorium coniiilex. Since it became apparent that iron would interfere seriously, it was dccided to eliminate completely all cations through the use of an ion exchange resin. Xielsen (8) also has reported the successful use of such method.
0 30
I
b
Y
\
Ot{
3
i
03j 0
2
I
FLUORIDE
0 0
0 001 0
I
2 FLUORIDE
3 CONCEHTRATION
-
I FRM.
5
Figure 3. Effect of changing ratio of color producing reagents
0 Feu.
mlphole
I eeM,RwMte
4
-
5
P?M.
Figure tion
5. Effect of iron on determina-
Table
II.
0 301
I
i
Determination of Fluoride Concentration
Found, P.P.11. _ _ _ ~ !ifc,gregianYhenylfluorone Naier met hod method
Fluoridc of phenylfluoroiie solution b e 4 satisfied the conditions imposed. This method, like most other methods for fluoride determination, 11as expected to suffer from interferences due to certain cations and anions. Experiments were undertaken to establish ivhich ions commonly found in sui face water r$ ould interfere. The bicarbonate ion was eliminated since its existence would be precluded by the pH of the medium. Sulfate and nitrate were not investigated because of their presence in appreciable amounts in the reagents used. The anions investigated Ivere phosphate and chloride. Chloride did not interfere up to a concentration of 100 p.p.m. The extent of the interference of phosphate is shown in Figure 4. This phenomenon may be due to the formation of thorium phosphate which would destroy the thorium-phenylfluorone lake. If phos-
3
CONCENTRATION
Present, 1' .P.XI. 1. 0 2.0 3.0
1.1 2.0
1 .o 1.8
2 $1
2.7
3001 2 FLUORlOE
3 CONCENTRATION
-
I P?M
Figure 4. Effect of phosphate ion on determination
., l o tcst the effectiveness of
the resin, a solution containing Fe(II1) ( 5 p.p.ni.). Ca(I1) (50 p.p.m.), pllg(I1) (20 p.p.ni.), Al(II1) (10 p.p.m.), RIii(I1) ( 5 p.p.m.), and fluoride (20 p.p.m.) was prepared. Fifty-milliliter portions of this solution were passed through the column, which has already been described. Analj-sis of three such samples gave 19.0. 19.5] and 19.0 p.p.m. of fluoride. This method is compared nith the Negregian-Maier method ( 7 ) in Table 11. Interfering ions present were those listed above.
LITERATURE CITED
(1) Urownlcy, F. I., Sellers, E. E., J . A m , W a t e r Tt-orks Assoc. 49, 1234 (1957). (2) Bumstead, H. E., Wells, J. C., .4sa1,. CHEM.24, 1595 (1952). ( 3 ) Curry, R. P., Mellon, RI. G.> Ibid., 28, 1567 (1956). (4) Damodaran, V., J . Sci. Ind. Research ( I n d i a ) 16B,366 (1957). (5) Fenton, H. J. H., J . Chem. Soc. l',xizs. 93, 1064 (1908). (6) Hines, E., Baltz, D. E., ASAL. CIIEX. 24, 947 (1952). ( 7 ) Megregian, S., Maier, F. J., J . Ana. W a f e r W o r k s -1ssoc. 44, 239 (1952). (8) Sielsen, H. XI,> ASAL, C H E l f . 30, 1009 (1958). RECEIVED for review December 14, 1959. Accepted June 16, 1960.
Determination of Piperazine as Piperazine Diacetate G. R. BOND, Jr. Houdry Process Corp., Marcus Hook, Pa.
b A rapid, yet accurate, method i s presented for the determination of the piperazine content of crude reaction mixtures encountered in its manufacture, as well as in its refined form. The method i s based upon ihe fact that piperazine is precipitated quantitatively and selectively (with the exception of certain of its homologs) from dilute solution in acetone upon
1332
ANALYTICAL CHEMISTRY
addition of at least the theoretical amount of glacial acetic acid required to form piperazine diacetate. cornOf the sample Other than piperazines either do not form pre-
ciPitates Or form Oils which are removed. This procedure has been used successfully to determine piperazine content ranging from 1 to 100%.
W
rapidly increasing use of piperazine and its salts in anthelmintics, antihistamines, surfaceactive agents, stabilizers, catalysts, and other pharmaceutical and agricultural products, the need has arisen for a rapid, yet accurate, method for the determination of the piperazine content of crude reaction mixtures encountered in its manufacture, as well ITH THE
as in the final product. h number of inetliods have been proposed for the determination of piperazine, such as through formation of the chromate (21, molybdate ( S ) , ferrocyanide, phosphomolybdate ( I ) , picrate, etc.; a rrcent technical bulletin (6) lists over 25 analytical referenws. However, pract,ically all these methods are restricted t o refined materials and serious interferences are introduced 1)y the presence of remaining portions of the raw materials (alkylene polyamines, alkaiiol amines, etc.) used in synthesis oi the piperazine and by various byproducts, such as pyrazines, triethylcwdiamine, etc., which niay be present in the crude material. Determinatioii by mass spectrometer, although effective, is time-consuming and requires expensive equipment. 1 simple, accurate, and rapitl iiietliod based on the quantitative and selccIT precipitation of pipcrazine from tiilutc solution in acetone upon addition of a t least the theoretical amount of glacial acetic acid rryuircd t'o form piperazine diacetate. This precipitate is in t8he form of bulky white crystals which can easily be filtered and washed on a sintered-glass filter! drictl a t room tt.inpcratiire in a vacuum desiccator, and weighed. Components of the samplc other than piperazines arv (tither not precipitated or form oils n.hich are removed upon n-ashing with acetone. Samples ranging from as little as 1 t o 1 0 0 ~ opiperazine have been analyzed successfully by this procedure. Otlier ketones, such as ethyl methyl ketone, and other fatty acids, such as formic or propionic acid, give similar results and may serve to dist.inguish lx~twcen thc various alkyl or Y-alkyl piperazines, but have not yet, been fiillp invesbigated. KO special Iahoratorj. eqiiipnient is required. PROCEDURE
%It the s;tmple in a rlosed container :it as 101% a temperature as possilde and -tir to assure uniformity. Since tliiq material 15 h~ groacopic and sublimes readily, avoid overheating or excessive exposure to the air. Carefully transfei 1.0 to 3 0 g r a m to a tared 11-eighing bottle, stopper quickly, and n eigli to the nearcst milligram. Dissolve the sample in a little acetone (acid-free) .iiid transfer to a 100-m1. volumetric flask using several small acetone rinses to ensure complcte transfer. In occasional saiiiple may he difficult to di-olve. In such caw, it niay be (lisqolved niore readilj 111 not niorr than 5 ml. of anhydrous methanol or ethyl dcohol, c.ompleting the dilution to the mark n i t h acetone. ?\lis thoroughly, transfer 25-ml. aliquots to 100-ml beakers find dilute each with an additional 25 nil. of acnetone. Add 0.35 to 1.05 ml of glacial acetic acid to each twaker (theory = 1.4 grams of acetic
acid per gram of piperazine), mix thoroughly with a small stirring rod, cover with a watch glass, and let stand a t least 5 minutes for complete precipitation. A large excess of acetic acid should be avoided. Filter through tared sintered-glass filters of medium porosity, rinsing the beakers and precipitates with four or five 5-ml. portions of acetone, using a policeman to transfer all the precipitate to the filter. Cut off the suction before each washing to ensure good contact of the acetone with the precipitate. Continue suction for 1 to 5 minutes to remove as much acetone as possible, then transfer the filters to a vacuum desiccator over sulfuric acid, cover with a protective shield, and evacuate t o 20 t o 28 inches of vacuum. Samples may usually be ~ e i g h e dto the nearest milligram after 15 to 20 minutes. The filtrate may be checked for complete precipitation b y adding 0.1 nil. niore of acetic acid and rubbing the walls of the beaker rvith the stirring rod to induce crystallization. Any precipitate should be added to the first lot.
TT
hctc IT' a 86
= wt precipitate in gram= u-t. samplr in aliquot = mol. wt. piperazine
20(i = mol. a t pijm-azinc iliac(.-
tate
DISCUSSION A N D EXPERIMENTAL RESULTS
Qualitative tests of tlir molybdate, chromate, and ferrocyanide methods on such materials as ethylrnediamine, diethylenetriamine. ethanolamine. and triethylenediamine, representative of possible impurities to br encountered in crude piprrazine, quickly s h o ed ~ that these materials inteiferc seiiously with attempts to determine piperazine. The addition of glacial acetic arid to an acetone solution of pipei azine cauqcd rapid and quantitative formation of a white crystalline precipitate wliich was idcntified as piperazine diacetate, both by the weight of material obtained from a known weight of piperazine and by titration of the precipitate in aqueous solution with standard hydrochloric acid, using 111 omophenol hluc indicator.
(3
.
H HOOC . C H -4
W
+
2CH3COOHH,HOOC'CH,
H
Table 1.
This precipitate was sul~stant~ially insoluble in acetone but readily soluble in alcohol or water. It had a melting point (sealed tube) of about 207" C. and sublimcd appreciably at 105" C.; therefore, acetone was removed by drying under vacuum at room temperature over sulfuric acid. Drawing air through the precipitate while on the filter aided in more rapid remoiral of most of the acetone. Addition of acetic acid to dilute solutions of ethylencdiamirie, diethylenetriamine, et~lianolamine, triethylenediamine, pyrazine, alkyl pyrazincs, pyridine, or 2-methyl-j-ethylpyridine in acetone caused either no precipitation or formation of a slight oily prvcipit'ste soluble in additional acetone. Solutions of 2-metliylpiperazinc, 2,j-dimethylpiperaxine, 2,6.dimethylpiper2,3.5,6-tetramethylpiperazine: azine. and ,V-niethylpiperazine in acetone formed at least partial precipit.ates with acetic acid, the last doubt'less being a monoacetate, but diphenylpiperazine, 1,4 - bis(2 - hydroxypropyl) - 2 - methylpiperazine, N-aminoethylpiperazine, or N,X'-dimethylpiperazine gave no precipitate. Hence, this reaction appears to be specific for piperazine and certain alkyl or mono N-alkyl piperazines. Precipitation of several of these alkyl piperazines is far from quantitative and some show even greater solubility when precipitated from chloroform solution n4icli may assist in giving more accurate> results for piperazine when alkyl piperazines arc present. Rit'li the except,ion of certain other fatty acids, as mentioned i:elow, no other acids tricd showed thr desired selectivity of precipitation. Ethyl methyl ketonc, chloroform, aiid possihly certain othrr ketones can be s u h s t i t u t d for awtone with fair success, although decreased solubility of piperazine in the higher ketones aiid loner volatility during removal of solvent, from the precipitate make them less convenient than acetone, while insolubility of samples containing water rules out chloroform in such cases. Likewise, with ethyl methyl ketone as solvent there is soinc precipitation with higher concentrations of tricthylenediamine. Fatt)y acids other than acetic acid were used for the precipitation of
Reaction of Fatty Acids with Piperazine Homologs in Acetone
Piperazine 2-Methylpiperazine 2,5-Dimethylpiperazine 2,6-Dimethylpiperazine 2,3,5,6-Tetramethylpiperazine
Formic Cryst. ppt. Partial ppt. Cryst. ppt. Partial ppt.
Fatty Acids Acetic Propionic Cryet. ppt. Yo ppt. Cryst. ppt. KOppt. Cryst. ppt. Cryst. ppt. Partial ppt. Partial ppt. Partial ppt. (forms slowly)
n-Butyric No ppt.
N o ppt.
Cryst. ppt
KOppt. x o ppt.
VOL. 32, NO. 10, SEPTEMBER 1960
1333
Table II.
Wt. piperazine, gram Vol. acetone, nil. Vol. H20,ml. Ratio H 2 0t o sample Wt. diacetate, gram Apparent purity, yo
Effect of Water on Determination of Piperazine as Diacetate
0.1925 50 0 0.461 99.9
piperazine homologs in acetone solution, as shown in Table I. This may afford a means of differentiating among these homologs. The effect of water in an acetone solution of pure piperazine on the determination by the diacetate method was studied (Table 11). Up to 47, volume of water can be tolerated in the acetone if the ratio of water to piperazine is not over 10 to 1 or u p to 67, water if the ratio is not over about 7 . 5 to 1. Thus, piperazine diacetate has a solubility (room temperature) of about 0.030 gram pri 100 ml. in 94% (volume) acetone. Because of the inconveniences of determining accurately the weight per cent rather than mole per cent of piperazine in crude reaction mixtures by mass spectrometer, very few samples have been run for comparison by both this and the diacetate method. In one case, a sample analyzed by mass spectrometei showed the presence by volume of about 34.3y0 piperazine, 3.47, alkyl piperazines, 40% triethylenediamine, over 47, pyrazines, and the balance alkylene polyamines, N aminoethylpiperazine, and related products. This corresponds roughly to 37.5% by 11 eight of piperazine or 41% total of piperazine plus alkyl piperazines. Analysis by the diacetate method gave 39.1% by weight, in very good agreement n-ith the mass apectrom-
0,1925 49 1 5.2:l 0,461 99.9
0.1925 48
a
10.4:l 0.459 90.6
0.1925 47 3 15.6:l 0.446 96.7
0.1925 46 4 20.8:l 0.427 92.7
0.1925 45
5 26.0:l 0.418 90.7
eter figures, considering the scanty knowledge of the behavior of all the alkyl piperazines. I n another case, analysis as diacetate gave 21.5% piperazine whereas the mass spectrometer gave 21.9%. Analyses of many other crude reaction mixtures have been confirmed by the subsequent yields of piperazine rccorered therefrom. A sample of iefined piperazine was determined by mass spectrometer, electrometric titration, and the diacetate method. Results in weight per cent were 98.0, 97.4, and 97.6, respectively. Another sample of refined piperazine was diluted rrith acetone and two aliquots were taken for analysis by the diacetate method. T o one aliquot, a weight of ethylenediamine equal to the weight of piperazine m-as first added. Substantially equal TTeights of piperazine diacetate were recovered from each aliquot. I n the absence of those alkyl piperazines which form cop1ecipitatps, this method is believed to be accurate to within 0.2’3, absolute. Where piperazine homologs are present, it is possible that they might be determined by titration of the mixed acetates in acetic acid solution with perchloric acid according to the method of Ciaccio et al. ( d ) , although such work has not yet been undertaken. Another possible qualitative or semiquantitative determination of the presence of alkyl
0.0385 47 3 78:l 0.077 83.5
0.0963 47 3 31.2:l 0.216 93.6
0.3850 47 3 7.8:l 0.915 99.3
piperazines is based on paper chromatography of the mixed acetates. using acetone containing a little water as developer and an ethereal solution of iodine to reveal the position of the spots. Piperazine catalyzes the convei sion of acetone to mesityl oxide, hence solutions should not be allowed to stand longer than necessary prior to analysis nor should they be heated above about 40’ C. while dissolving the sample. Re-analysis of solutions which had stood about 4 months gave only half the original piperazine value, showing that some reaction had occurred. ACKNOWLEDGMENT
The author wishes to thank t,hv Houdry Process Corp. for permission to publish this method. LITERATURE CITED
(1)Castiglioni, A., Nivoli, M., Z urrtri. Chem. 133, 193-4 (1951). (2)Ibid., 138, 186-7 (1953). (3) Castiglioni, A,, Vietta, M., I h a d . 142, 18 (1954). (4) Ciaccio, L. L., Missan, S. R., XlcMullen, Grenfell, T. C., AXAL.CHEM. 29, 1670-2 (1957). (5) Jefferson Chemical Co., Techniral Bull.on Piperazine, 1957.
RECEIVEDfor review March 14, 1960. Accepted June 6, 1960. Delaware Valley Regional Meeting, ACS, Philadelphia, Pa., February 1960.
N e w Rapid Vacuum Fusion Apparatus for Determining Oxygen in Titanium and Steels L. C. COVINGTON and S. J. BENNETT Process Research Division, Titanium Metals Corp. o f America, Henderson, Nev.
,A simplified vacuum fusion apparatus consists of a small resistanceheated furnace, an efficient pumping method, and duplicate analytical systems. When operated using the platinum flux technique, this apparatus with a single operator is capable of completing 75 oxygen determinations in each 8-hour shift. Data are given to prove a high degree of precision and accuracy when applied in a routine manner to titanium alloys and to steel.
1334
ANALYTICAL CHEMISTRY
T
determination of oxygen has become increasingly important because of its effect on the physical properties of metals. Of the methods currently in use, vacuum fusion ( 3 ) has gained the widest acceptance, although it has been slow and expensive and otherwise unsuitable for control analyses. Further m-ork (.2) has indicated that, under proper conditions, the vacuum fusion reaction is extremely rapid. The use of a new resistance-heated furHE
nace, an efficient gas transfer system. and the platinum flux technique ( 4 ) has permitted full utilization of the inherent speed of this reaction. APPARATUS
The apparatus designed and developed b y Titanium Metals Corp. of America (patent applied for) is illustrated in Figures 1 and 2 . The apparatus consists of a furnace section, a power supply, a n analytical system,
