ANALYTICAL CHEMISTRY
1794 Both correspondents also question the melting point of 220" C. given in the original description for 4-aminosalicylic acid. T h e value of 220" C. is, however, correct, although mention should have been made that this value was obtained on the Kofler hot bar before significant decomposition had occurred (in 3 seconds from the time the sample is placed on the bar). This compound
decomposes extremely rapidly, as indicated by the fact that the melting point measured 10 seconds after the sample is placed on the hot bar is already down t o 190" C. T h e figure of 3 seconds chosen is the time required for finely ground crystals of a thermally stable compound to exhibit its known melting point.
W.C. MCCRONE
SCIENTIFIC C O M M U N I C A T I O N
Identification of Amines as Tetraphenyl borates SIR: We have found that basic organic nitrogen compounds as well as their salts can be detected by precipitation of their tetraphenylborate compounds in aqueous acid solutions. A simple potentiometric method for determining the tetraphenylborate ion [ (CaHr),B-] contents of these salts has been developed. Such analyses together with melting point values provide a new, rapid way of identifying basic amines. Sodium tetraphenylmetaborate (Na T P B ) is known to precipitate quantitatively potassium and ammonium ions as well as certain alkaloids from aqueous hydrochloric acid. A comprehensive bibliography has been reported recently on this subject by Barnard (1). Schultz and Goerner (9) found that quantitative determinations were possible with certain alkaloids in the 100-mg. range. blarquardt and T'ogg (6) showed t h a t the tetraphenylmetaborate derivatives of choline and acetylcholine hydrochloride had sharp melting poicts, after recrystallization from acetone. Zeidler ( l a ) reported that the alkaloidscadaverine, histamine, histidine, guanidine, putrescine, and spermine-yielded tetraphenylmetaborate precipitates, which possessed rather sharp melting points even without recrystallization. We have found that this reaction has wide application. Any organic amine, which is basic enough to place a positive charge on its nitrogen atom, can be precipitated with 0.6% sodium tetraphenylmetaborate solution from aqueous solutions of its hydro or quaternary halide salts as its tetraphenylborate derivative. I n fact, the results obtained from testing about 120 mater- and acid-soluble organic compounds, covering all possible functional group types, indicate that sodium tetraphenylmetaborate can be used to test qualitatively for basic nitrogen compounds. T h e test is very sensitive as well as specific. I n the
NO.
1 2
3 4 5 6 7 8 9
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
case of methyl-4-picolinium iodide, a precipitate is detectable a t a concentration as l o x as l O - 5 X , after centrifuging. This compound was precipitated quantitatively in the 0.4- to 1.O-mmole range. A study of the stoichiometry of the reaction between sodium tetraphenylmetaborate and other nitrogen compounds is now in progress. MATER1 4LS
T h e sodium tetraphenylborate (reagent grade) Tvas purchased from the J. T. Baker Chemical Co. and used directly. T h e potassium tetraphenylborate was prepared according to the procedure recommended by Sporek and Williams (10). Tetra-n-butylammonium bromide was prepared according to the procedure of Sadek and Fuoss (8). T h e colorless crystals melted a t 118-20" C. Methylpyridinium iodide, melting point 123-5", and 1,2-(di-P pyridy1)-ethane, melting point 114.5-16.0", &-ere synthesized and recrystallized according to Bergmann, Crane, and Fuoss (3). Methyl-4picolinium iodide, melting point 157-8', and 2iodoethylpyridinium iodide, melting point 108-lo", were prepared according to Crane and Fuoss (3). Tetramethylammonium iodide n-as prepared by the usual addition of methyl iodide to trimethylamine. Excess alkali was added to a n aqueous solution of trimethylamine hydrochloride, and the free amine bubbled into 95% ethanol, immersed in ice water. Half as much volume of cold ether was added, followed by a 50oJ, molar excess of methyl iodide. White crystals soon began to form a t 10". After the reaction had subsided, th: vessel plus contents was allowed to stand for 10 hours a t 25 After filtration and three 20-ml. washes with cold ether, glistening Jyhite crystals, melting above 230", were obtained. Methylquinolinium iodide was obtained b y . the addition of 30 grams of methyl iodide to 15 grams of redistilled quinoline in 40 ml. of ether. T h e mixture was allowed to stand 24 hours a t 25" in the dark in a rubber-stoppered flask. T h e orange solid was separated by filtration and washed with absolute ether. Recrystallization from benzene yielded yellow crystals. meltinn a t 133'. A s a m p l l of 2,2'-dipyridylamine was synthesized according to Tschitschibabin's proTable I. Compounds Showing No Reaction with Sodium Tetraphenylborate cedure (11). T h e starting No. Compound Structure Type Compound Structure Type material, crude 2-aminopyriAcid Citric acid Benzyl chloride Hydrocarbon 26 dine, A, was obtained from Acid Succinic acid Alcohol 27 Methanol the Reilley T a r and Chemical Acid p-Hydroxyhenaoic acid 28 Ethanol Alcohol Corp. Condensation of equal Acid p-Toluenesulfonic acid Alcohol 29 2-Propanol Amide Urea 30 2-Methyl-2-propanol Alcohol molar amounts of compound Amide Thiourea Alcohol 31 Ethylene glycol A and its hydrochloride salt Ester n-Butyl formate 32 Alcohol Glycerol (prepared by bubbling anhyEster E t h y l acetoacetate Phenol Phenol 33 Sugar Dextrose Phenol 34 p-Nitrophenol drous hydrogen chloride into Sugar Fructose 1-Naphthol Phenol 35 a n ethanol solution of A, Lactose Sugar Phenol 36 Resorcinol followed by evaporation of Maltose Sugar 37 Phenol Hydroquinone Sucrose Sugar Ether 38 Z,Z'-Dihydroxyethyl ether the solvent) a t 240' in the Alizarin sodium sulfonate Quinone Ether 39 Heliotropin absence of moisture gave a Azoxybenzene AZO 40 Ether Paraldehyde 25% yield of the desired 2,2'Methyl orange .bo Ether 41 Ethyloxonium chloride Ethanolamine Amjne 42 Aldehyde Formaldehyde dipyridylamine. Crysta 1li z aTrishydroxymethylaminomethane Amine 43 Chloral hydrate Dihydroxy tion from hot water gave long Hydroxylamine hydrochloride Amine 44 Ketone Acetone Semicarbazide hydrochloride Amine white needles, melting a t 95". Ketone 46 Methyl ethyl ketone p-Nitrophenylhydrazine Amine 46 Acid Formic acid Methyl d i e t h y 1s u l f o n i u m 2,4-Dinitroaniline Amine 47 Acid Acetic acid iodide was prepared by the d,l-Alanine Amino acid 48 Acid Lactic acid Sulfanilic acid Amino acid addition of a 70% molar ex49 Acid P ruvic Acid Sodium sarcosinate Amino acid 50 Acid T3;ioglycolic . acid cess of methyl iodide t o 8 grams of diethyl sulfide in 30
V O L U M E 2 8 , N O . 11, N O V E M B E R 1 9 5 6 Table 11.
Compounds Yielding White Precipitates Immediately a t 25" with Sodium Tetraphenylborate
51 52 53 54 55 56 57 58
Compound A. Quaternary Ammonium Salts Tetramethylammonium iodide Tetrabutylammonium bromide Tetraethanolammonium hydroxide Betaine Methylpyridinium iodide Methyl-4-picolinium iodide N-2-lodoethylpyridinium iodide hfethylquinolinium iodide
59 60 61 62 63 64 65 66 67 68 69
B. Heterocyclic Amines Pyridine 2,2'-Dipyridylamine Quinoline 8-Quinolinolc 1,2-Di-(4-pyridyl)ethane %Met hylpyrazine 2,s-Dimethylpyrazine Piperidine Hexamethylenetetramine Caffeine Creatinine
No
I
1795
Melting Points of PrecipiNo. tates, C.
Compound E. Tertiary Aliphatic Amines 81 Trimethvlamine 82 Triethylamine 83 Triethanolamine 84 Dimethylbenzylamine 85 Methyldibenzylamine
-4bove 360 229-3lU 160-62 118-19 5 242-3 201-4
Melting Points of Precipitates, C. 170-2 172-4 143-5 182-5 140-2
F. Primary .4romatic Amines
196.5-9.5
86 87 88 89 90 91 92 93 94 95 96
229-31.5 179-83 135-7 199-202n 171-8 141-4 160-1 128-9 143 . 0 - 3 . 5
Aniline p-Bromoaniline p-tert-Amylaniline p-Methylaniline o-Methylaniline o-Methoxyaniline 1-Naphthylamined 2-Naphthylamine p-Hydroxyanilinee o-Phenylenediaminef m-Phenylenediamine
125.5-8.5 92.5-7.5 b 146-9 141,554 119-21 123-5 111-13 b 138.5-40.5 b 105-8 140-4 116-21
ml. of ether. After 3 d a w an orange oil had separated"from the cloudy solution. The oil was separated from the ether solution in a separatory funnel and was washed with four 10ml. portions of ether. Some of the sulfonium iodide, thus obtained, was dissolved in water, without further purification, for testing purposes. The remaining organic compounds, which were tested, were commercially available products. Whenever necessary, they were purified by recrystallization or simple distillation t h r o u g h a V i g r e u x column. PROCEDURE
Amine Detection. The qualitative tests are conducted by 97 dissolving 5 to 10 mg. of the 98 C. Primary Aliphatic Amines organic compound in water or 6,V hydrochloric acid, adjusting Methylamine hydrochloride 209-11 H. Tertiary Sromatic Amines 70 Ethylamine hydrochloride 163-9 71 the p H a t 2 to 3, and then 99 N,A'v'-Dimethylaniline 121-4 Butylamine hydrochloride 72 diluting to approximately 5 ml. 126'5-8'5 100 p-Broniodiethylaniline 111-26 121-3' Glycine methyl ester 73 178-182a 101 p-Dimethylaminobenzaldehyde A 0.670 aqueous solution of Benzvlamine 74 2-Phenylethylamine 173-5 75 sodium tetraphenylborate is I. Quaternary Onium Salts prepared according to the proD. Secondary Aliphatic Amines 102 Methyldiethylsulfonium iodide 177-9 cedure of Gloss ( 4 ) . A small Dimethylamine 157-61 103 3-Benzylthiuronium chloride 181-2 76 portion (1 to 2 ml.) of the Diethylamine 169-70 77 latter solution is added to the Diisopropylamine 155-6 78 144-5 Dihutylamine 79 5 ml. of the former. The imDibenzylamine 129-33 80 mediate formation of a dense. usually x h i t e precipitate indil a Melts repeatedly at this temperature. d Pink precipjtate. 6 Brown precipitate. b Compound unstable. cates the presence of a salt of c 17ellow precipitate. i Red precipitate. a basic amine. Amine Identification. For melting point and analysis Table 111. Data Obtained in Potentiometric Standardizastudies, the borate solution is tion of Silver Sitrate with Potassium Tetraphenylborate added slowly tTith stirring to a (109.8 mg. of I< T P B in 100 ml. of 1: 1 aqueous acetone 9.0 mmole each of 10 to 207, excess (ca. 0.2 gram) of the amine dissolved in 15 to acetic acid and sodium acetate bufferj 20 ml. of hydrochloric acid solution, which has been adjusted to a p H of 2 to 3. The tetraphenylmetaborate precipitate is reSilver N i t r a t e , AT', AE, lf\7, , y x l O - ' $;,,, M1. E , blv. M1. moved by suction filtration, washed well with distilled water, and dried below 60'. A melting point of the tetraphenylme0,000 460 4.993 498 taborate derivative serves to identify the original amine. A 507 5.060 Purdue melting point tube, filled with a high boiling petroleum 0 035 13 3.7 5.078 oil, was used in this laboratory. 5,095 520 20 5.115 5.0 0 040 The tetraphenylborate derivatives were analyzed for nitrogen 540 5.135 by the conventional Dumas method; and for tetraphenylmeta0 020 15 5.149 7.5 borate ion content by a new potentiometric method, which is 555 5.155 35 0 025 14.0 5.168 based on the insolubility of silver tetraphenylmetaborate in 590 5,180 aqueous acetone. Two recent methods for determining potas0 025 75 30.0 5.193 sium are also based on this fact. Rudorff and Zannier ( 7 ) 5.205 665 5,220 0 030 80 26.7 added a known excess of 0.05N silver nitrate to the potassium 5,239 749 tetraphenylmetaborate in acetone, and back-titrated with thio0 032 5.251 70 21.9 cyanate according to the Volhard procedure. Hahn ( 6 ) titrated 5.267 815 5.284 0 033 45 13.6 the potassium ion in aqueous solution directly with standard 5.300 860 silver nitrate using chromate indicator via the Mohr method. 5.315 0 030 21 7.0 Our potentiometric method consists of dissolving the tetra5.330 881 phenylmetaborate samples (0.2 to 0.4 meq.) in ca. 90 ml. of 1 to 1 aqueous acetone. A mixture of 3.0 ml. of 3M acetic acid and 3.0 ml. of 3 M sodium acetate is added to buffer the solution. Table IV. Potentiometric Titration of LMethylpyridiniumThe resulting solution is then titrated with 0.06N aqueous silver tetraphenylborate with Silver Nitrate nitrate, using a Beckman p H meter, a silver wire indicator, and a AE, 10-2 Vol., Vol., E, glass reference electrode to measure the e.m.f. changes. The hI1. hI.7. hlv. M1. silver nitrate is standardized against potassium tetraphenylborate 4.67 810 which has been reprecipitated from acetone. 0.05 9 1.8 4.70
yvx
3
4.72
819
4.75
826
4.77
848
4.79
909
4.81
1085
4 83 4 85
1110 1145
4.88
1170
4.92
1180
G. Secondary Aromatic Amines N-Methylaniline 105-16 Phenylhydrazine 144-7a
0.03
7
2.3
4.74
0.02
22
11.0
4.76
0.02
61
30.5
4.78
0.02
176
88.0
4.80
0.02
25
12.5
4.82
0.02
35
17.5
4.84
0.03
25
8 3
4.87
0.04
10
2.5
4.90
DISCUSSION
The immediate formation a t 25' of a dense, usually white, precipitate, upon addition of the tetraphenylborate ion to an aqueous solution, establishes the presence of a basic amine ion, providing certain interfering cations are known to be absent. The inorganic cations-potassium, rubidium, cesium, ammonium, and mercuric ions-also yield precipitates ( 4 ) under the conditions of the test. As Table I shows, sodium tetraphenylborate is without effect on uncharged organic compounds. Of all cations (see Table 11) that gave a positive test, only two contained their
ANALYTICAL CHEMISTRY
1796
of these derivatives melt with decomposition, the ranges are sharp enough and of a suitable temperature (somev-here between 90" and 240") to identify the amine. Although the original tetraphenylborate precipitates need not berecrystallized or purified further for identification purposes, some can be recrystallized from aqueous methanol or acetone. However, several underwent decomposition when warmed in these solvents. Thus, because they are so easily prepared and do not need to be recrystallized, tetraphenylborates are superior to other derivatives commonly used to identify basic nitrogen compounds. Also, the melting points of these tetraphenylborate derivatives are indicative of and sensitive to slight structure variations. For example, introduction of a p-methyl group on the pyridine ring (see compounds 55 and 56 of Table 11) lowers the melting point about 40". Placement of an 8-hydroxy group on the quinoline nucleus (see compounds 61 and 62) raises the melting point 64". -4s illustrated by compounds 70 through 7 2 , a n increase in the length of the carbon chain is accompanied by a distinct drop in the melting point. The sensitive effect of the position of a substituent group on the melting point of an aromatic amine is exhibited by compounds 89, 90, 92, 93, 95, and 96. T h e potentiometric determination of tetraphenylhorate ion is based on the stoichiometric completeness of the reaction:
Table V. Comparative Slopes in Potentiometric Titration of Tetraphenylborate Salts with Silver Nitrate Compound Llethylpyridinium T P B Diethylamine T P B Glycine methyl ester T P B Sodium tetraphenylborate Hexamethylenetetramine T P B Potassium tetraphenylborate Anilinium tetraphenylborate
Table VI.
Equiv. Pt., RI1. 4.800 5,636 6.058
Slope. Max. 88.0 62.5 40.0 35.0 33 3 30.0 4 3
4.546 5,213
Analysis of Tetraphenylborate Derivatives
Original Compound
Tetraphenylborates RI.~., (CsHdrB, 70 C.a Calcd. Found
Tetraethanolainmonium 160-2 hydroxide Tetra-n-butylammonium 229-31 bromide 117-8.5 Betaine Methylquinolinium io196-9 dide Hexamethylcnetetrani160-1 ine 170-2 Trimethylamine 169-70 Diethylamine 209-1 1 Methylamine 126-9 Aniline a Corrected values. b Slope so poor t h a t no definite end true f o r primary aromatic amines.
Xitrogen, % Calcd. Found
61.7
60.7
2.69
56.0 73.1
55.9 73.8
...
68.9
69.8
69.3 84.2 81.2 90.9 78.0
69 5 82.6 80 6 89 5 b
point was detected.
3.21 2.96 12 3 3 4 3
16 70 57 00 42
2.73
...
3.35 3.05 12.09 3.69 3.71 4.52 4.33
This is generally
.4g+
r+f
B(C&)d-
-,Org NB(C&)r 4
where Org K can be an ammonium ion in any of the four possible stages of subst'itution-Le., RNH, +, RR'NHz+, RR1R2S"+, or RR1R2R3X+. The radicals, R through R3, may be alike or dissimilar. The results also show that only amines, >Those basic ionization constant is a t least as great as 1 X IO-", can yield precipitates 90r +
immediately a t 25". For example, aniline hydrochloride reacts immediately, whereas the introduction of one negat,ive nitro group in the benzene ring causes p-nitroaniline to react so slowly that only a few crystals of the tetraphenylborate derivative form after long standing. When two nitro groups are present, as in 2,4-dinitroaniline, no precipitate whatever is formed. The presence of solubilizing groups in the amine ion also hinders the format,ion of a precipitate. Only small quantities of tetraphenylborate precipitate are obtained from large amounts of p-hydroxyaniline; and the solubility product was not even exceeded in the cases of ethanolamine and trishydroxymethylaminomethane. Because triethanolamine is of higher molecular weight, i t is readily precipitated. The introduction of a met,hyl group into the structure of glycine to form its methyl ester (compound 7 3 of Table 11) was found to decrease the solubility of the tetraphenylborate derivative enormously. Whereas three amino acids ( S o s . 48, 49, and 50 of Table I) gave no precipitates under any conditions, p-aminobenzoic acid, I-proline, l-tyrosine, dl-serine, dlaspartic acid, and Z-cysteine hydrochloride will yield white precipitates, if the solution is heated. I n Table I1 are recorded the melting points of various tetraphenylborate derivatives. While most
&B(C&)a
4
in 1 to 1 aqueous acetone solution. Typical data ohtained in titrations with aqueous silver nitrate solution are listed in Tables I11 and IV. The column headings stand for the following: Yol, is milliliters of silver nitrate solution added; E is the electromotive force in millivolts; AV is the increment of volume; AE is the increment of electromotive force; and A E / A l y is the rat? of change of E with silver nitrate added. When the values are plotted against silver nitrate added, of AE/AV X the maxima of the -graphs locate the equivalence points. Figure 1 shows the differential curves obtained by titrating some representative tetraphenylborate derivatives with silver nitrate solution: hexamethylenetetramine, methylpyridinium, potassium, diethylamine, and glycine methyl ester. The maximum values of the slopes obtained experimentally for t,hese deriva-
positive charge on an atom other than nitrogen. These interfering onium salts are methyldiethylsulfonium iodide and Sbenzylthiuronium chloride. As Table I1 indicates, all possible types of basic amines yield precipitates, The size or shape of the cation does not appear to be a critical factor. The general reaction can be formulated: Org
+ (C&shB--
I
1
1
,
L
80
I
* g x
1
c
7 -
60
-
50
r -
-
70
--
-
2 $ 40 30
+.
L
10
I
0 4.0
4.5
l
!
5.5
5.0
VOLUME
OF
6.0
AgN03, ML.
Figure 1. Differential potentiometric plots of titration of tetra-. phenylborates with silver nitrate G. Hexamethylenetetramine Methylpyridinium Potassium E. Diethylamine 6'. Glycine methyl ester
P. K.
V O L U M E 2 8 , NO. 11, N O V E M B E R 1 9 5 6 tives as well as for sodium tetraphen:-lborate and anilinium tetraphenylborate are recorded in Table T', which also lists the estimated equivalence points. These data indicate that, the slopes at' the equivalence point are greatest for the heterocyclic and aliphatic amine borates, and steep enough to make possible the detection of an end point for all other types except the primary aromatics (represented hy the anilinium derivative). T h e nitrogen and tetraphenylhorate analyses for a series of represent'ative derivatives are listed in Table VI. An examination of the data indicates that only one tetraphenylborate group adds per molecule of amine, regardless of the number of nitrogen atoms present. For some 25 compounds analyzed, the values for tetraphenylborate found were within 3% (relat,ive) of theory. These v:iluc,s were reproducible to a relative precision of 0.3%.
1797 der, which is pelletized. A critically damped multisource dihcharge is used initially to spark the pellet and the resultant spectrum is recorded. The pellet is then arced with a heavily overdamped discharge and the resultant spectrum is separately recorded. Densitometered spectral lines are used to prepare working curves for the individual elements sought. Generalized Working Curves for Both High- and Low-Alloy Steels. L. 0. EIKREM, Baird Associates-dtomic Instrument Co., Cambridge. Mass.
Both high- and low-alloy steels may he analyzed from the same analytical working curves when atomic dilution theory is properly applied. This procedure assists considerably in establishing working curves, inasmuch as separate sets of standards for each alloy type need not be prepared. The paper demonstrates the establishment of generalized working curves by use of the (M X ) factor previously reported. 41 is the concentration of the matrix element, and X is the concentration of the element being analyzed. Points obtained with standards are translated vertically to a constant (31 X ) value in accordance with the equation:
+
+
ACKNOW LEDGM EVT
This nork was made possible by a Cottrell grant from the Research Corp., Ken- Tork, S . Y.and by a grant from the Rutgers Cniversity Research Council. The author thanks E v a Agnes Smith for assistance in the experimental work.
X'
=
x (JI'
X')/(.11
+X)
Curves for the various elements need not be plotted at the same (X X ) value. The concentration values, X', for the various elements as read from the curves are used to solve for actual concentrations, X, using the formula:
+
LITERATCYRE CITED
Barnard. A. J., Chemist-Analyst 44, 104 (1955). Bergmaiin, E. D., Crane, F.E., Fuoss, R. I f . , J . A m . Cherri. Soc. 74, 5981 (1952). C'rane, F. E., Fuoss, R . II.,. ~ N A L .CHEM.26, 1651 (1954). Gloss. G . H., Chemist-Amlysf 42, 55 (1953). Halin. F. L.. Z. ana!. Chem. 145, 97 (1955). .\Iarquar.dt, P., Vogg, G., Hoppe-Seyler's 2 . physiol. ChenZ. 291,143 (1952). Rtidorff. W.,Zanuier, H.. Angetc. Chena. 66, 638 (1954). Sadek, H.. Fuoss, R . M., J . B i n . Chem. Soc. 72, 301 (1950). Schultz. 0 . E., Goerner, H., Deuf. Apofh.-Ztg. ver. Suddeut. Apotli. Zlg. 93, 585 (1953). Sporek. K., Williams, A. F.. Analyst (London) 80,347 (1955). Tsrhitsc.hibabin. V., Ber. 61B, 199 (1928). Zeidler. L., Z . p h y s f o l . Ciiem. 291, 177 (1952). Douglass College Chemistry Laboratory Rutgers Unimrsity New Brunswick, N. J.
FRAXCISIE. CR.4NL, JR.
R E C E I V Efor D review March 6. 1956. Accepted A u g u s t 6, 1956. Presented in part before t h e Analytical Division, .\Ieeting-in-~Ziniature, North Jersey Section, AC'S, South Orange, N.J., January 30, 1936.
M E E T I N G REPORT
Third Ottawa Symposiwm on Applied Spectroscopy Ottawa Symposium on Applied Spectroscopy was TheldThird Sept,ember 12 t o 14 in Ottawa under the auspices of the HE
Ottawa Valley Section of the Canadian ilssociation for Applied Spectroscopy: with the cooperation of the Mines Branch and the Geologies1 Survey Branch, Departmen't of Mines and Technical Surveys. Abstracts of the technical papers presented are given here.
Xi' x,=1 100 + n xi' ~
-7
L 1
in which x,' = X i ' / ( K i ' - Xt')
+
Iii' represents the value of (.I1 X ) for the element i curve. The calculations are quickly made iyith the help of appropriate tables and a calculating machine. When a large number of analyses of the same alloy type must be made, individual curves for each type may be set up to read actual concentration directly, although the standards used in setting up these curves may represent a variety of alloy types. Comparative direct reader and wet chemical results were shown for a number of highblloy types. including stainless. Coefficients of variation of 1% or better of the amount present between direct reader and chemical values for the high concentration elements are readily obtainable. Spectrographic Sample Forms in Use at a Copper and Brass Mill. P. R. DE LHORBO, .-inaconda .Imerican Brass, Ltd.. S e w Toronto, Ontario. Sample forms have been developed to meet changing requirements of casting shop, mill, and miscellaneous materials such as scrap and fabricated parts. An analytical procedure using a laboratory cast pin sample was described in detail. Spectrographic Determination of Impurities in Selenium. N. TOMINGAS A N D W. C. COOPER,Canadian Copper Refineries, Ltd., Montreal, Quebec. Rapid and accurate spectrochemical procedures for the estimation of impurities in refined and high purity selenium were described. In
the analysis of high purity selenium external comparison standards, which have been evaluated by accurate chemical methods, are employed. The use of such standards permits the rapid routine analysis of large numbers of samples. Mercury and tellurium in refined selenium are estimated densitometrically. A split filter of 10 and 100% transmission enables the use of selenium as internal standard and the determination of tellurium in the range 0.01 to lye. The agreement with chemical analyses is excellent.
Spectrochemical Analysis of Lead Alloys. J. H . D. HOWARTH ASD H. NAUSESTER, Canada Metal Co., Ltd., Toronto, Ontario. The behavior of various alloying elements under a number of difficult analytical conditions has been studied. Some of the problems of this type of analysis mere discussed and a suggested method of analysis was outlined.
Segregation Studies in Titanium Alloys by the Spectrographic Microvolume Technique. J. K . HURWITZ,Mines Branch, Ottawa, Ontario. Segregation occurs in titanium alloys coutaining 4% manganese and 4% aluminum as well as 6% aluminum and 4% vanadium. Samples of these alloys were analyzed by the spectrographic microvolume technique and major segregation of the alloying constituents was found.
Spectrochemical Analysis of Corrosion Products on Lead Sheath of Cables. W. J. BEXNETT,Northern Electric Co., Ltd., Lachine, Quebec. Products adhering to lead sheaths, usually in small amounts, were analyzed to determine major and minor components. The method utilizes a mixture of sample, germanium dioxide, and graphite pow-
Standards for Spectrographic Analysis of Magnesium and Its Alloys. L. R. PITTWELL, Dominion Magnesium, Ltd., Haley, Ontario. The dangers of indiscriminate use of purchased standards arise from variation in shape between standard and sample and differ-
