ANALYTICAL CHEMISTRY
294 grade Type A material [no octahydro-1,3,5,7-tetranitro-s-tetrazine (HMX) present] from acetone until a corrected melting point of 201” C. was obtained. I n the original survey of the problem of titrating composition ‘2-4, several approaches were attempted with little success. One method involved the direct titration of composition C-4 in dimethylformamide. This resulted in low, erratic results characterized by drifting, indefinite end points. These were undoubtedly due to the occlusion of hexahydro-1,3,5-trinitro-s-triazine crystals by the polyisobutylene binder, which prevented complete solution in dimethylformamide. .4 second approach involved the extraction of the binder with carbon tetrachloride, removal of the carbon tetrachloride with the aid of a filter stick, and direct titration of the hexahydro-1,3,5-trinitro-s-triazineafter addition of dimethylformamide. Of necessity, the sample weight for this procedure was in the order of 0.3 gram. While sharp end points were ebtained, the precision of this procedure was far from satisfactory when applied to plant samples. Synthetic samples, on the other hand, gave good precision. It soon became apparent that the hexahydro-l,3.5-trinitrc-s-triazine content of individual 0.3-gram samples varied by as much as 59$ This error, probably due to nonuniformity of the sample was overcome by increasing the sample Reight to 1.5 grams, and aliquoting. Using this procedure the results obtained on plant samples of composition C-4 gave good precision. RESULTS
The nonaqueous titration method has been applied t o samples of purified hexahydro-1,3,5-trinitro-s-triazine containing no
octahydro-1,3,5,7-tetranitro.s-tetrazine(HAIS) and synthetic samples of compositions A-3 and C-4 (Tables I, 11, and 111). I n view of the average standard deviation of 0.13% and the average error of 0.13% obtained, as well as t,he simplicity and rapidity of the developed method, it is recommended t h a t the method be incorporated in applicable government and industrial specifications for the determination of the purity of hexahydrc1,3,5-trinitro-s-triaxine and its content in explosive compositions. ACKNOWLEDGMENT
The author wishes to express his appreciation to E. F. Reese, A. J. Clear, C. J. Bain, Robert Frye, and J. D. Armitage of Picatinny -4rsenal for help rendered in the preparation and publication of this report. Appreciation is further expressed to the Ordnance Corps for permission to publish this paper. LITERATURE CITED
(1) Bellini, Ann. chim. appl., 31,125-9 (1941). (2) Desvergnes, Chimie & industrie, 28, 1 0 3 8 4 4 (1932). (3) Fritz and Lisicki, AKAL.C m x , 23, 589 (1951). (4) Jones and Thorne, Can. J . Research, 27B,828-60 (1949). (5) Kouba, Kickelighter, and Becker, A N ~ LCHEM., . 20, 948 (1948). (6) Rathsburg, Ber., 54B,B183-4 (1921). (7) Schroeder, Wilcox, Trueblood, and Dekker, ANAL.CHEM.,23, 1740-7 (1951). (8) Soldate and Noyes, Ihid., 19, 442-4 (1947). (9) Ternazra, Chimica e industria ( M t l a n ) , 17, 686-7 (1935). (10) Wright, Holston Defense Carp., Control KO. 20-T-17, Series A, 6 July 1953, Kingsport, Tenn.
RECEIVED May
1 0 , 1954.
Accepted September 30, 1954.
Estimation of Metallic Mercury on the Surface of Tinned Copper G E O R G E T. KERR, SYLVESTER S. MACUT’, and C A R L C. NEELY2 Aircraft-Marine Products Inc., Harrisburg, Pa.
An evaporation method has been developed whereby 0.3y0 of mercury can be estimated on tinned-copper samples weighing approximately O.? gram. Accuracy was ascertained by using specially prepared samples containing known quantities of mercury. For samples containing in the order of 2 mg. of mercury, the average difference between the known and estimated content was 10.21 mg., or an error of approximately &lo%. Application to quality control is promising.
T
INNED-copper bodies are produced in quantity for use as various types of contacts in electrical industries. It has been found that “tumbling” these bodies with mercury forms a tin amalgam giving a much improved electrical contact. As a n excess of mercury results in the eventual amalgamation and breakdown of copper, it is important that the quantity of mercury deposited on each piece be controlled. Approximately 0.3 to 0.5% of mercury per sample, depending upon the shape of the body, gives excellent results electrically. However, each sample weighs approximately 0.7 gram. Thus, determining t h e quantity of mercury per sample for a large number of samples utilizing conventional methods would have been tedious. T h e amalgamation method (1,8 ) for determining mercury was considered. This consists in chemically reducing mercury compounds t o metallic mercury, vaporizing the metal, and condensing the vapor on B cooled, tared strip of silver. T h e mercury is Present address, Medical School, Temple University, Philadelphia, Pa. Present address, College of Chemistry and Physics, The Pennsylvania State University, State College, Pa. 1 2
thus weighed directly. In the present problem, chemical reduction would not be necessary, as the mercury is present as the metal. This method was not promising for a large number of analyses, but it led to the development of a similar procedure. EXPERIMENTAL
One hundred tin-plated copper samples, each weighing approximately 0.7 grams, were numbered u i t h a metal punch for identification, and were individually weighed to the nearest 0.1 mg. using a conventional analytical balance. The weighings were made by a technician with no previous weighing experience. The pieces were placed in a 250-ml. glass-stoppered Erlenmeyer flask and “tumbled” for 1 hour. Six samples mere chosen at random and reweighed. The average weight loss was less than 0.1 mg.; the maximum weight loss amounted to 0.2 mg. To the 100 samples was added 0.2000 gram of mercury. The samples were tumbled with the mercury for 1 hour and again weighed to the nearest 0.1 mg. The data showing weight of mercury deposited on each sample are listed in Table I. The total weight of mercury detected amounted t o 0.1863 gram as compared Kith 0.2000 gram, the amount actually used. Thus the average error is -0.14 mg. per sample, probably attributable to weighing errors. Apparatus. -4250-ml. round-bottomed flask is fitted to any laboratory-type vacuum pump capable of producing 1 mm. of pressure. The pump is protected with an ice trap. I t is preferable that the flask be fitted with either spherical or standardtaper lass joints. The flask is heated in an oil bath containing Dow-&orning silicone oil S O . i 1 0 . Test Procedure. The 100 specially prepared mercury-coated samples were placed in the flask and the system was evacuated to 1 mm. of pressure, Meanwhile, the oil bath was heated on an electric hot plate to 190’ C. This temperature should be sufficient to effect complete mercury removal a t 1 mm., since the vapor pressure of mercury a t 190” is approximately 12 mm. The flask and contents were immersed in the bath t o a depth
V O L U M E 27, NO. 2, F E B R U A R Y 1 9 5 5 Table I. Difference
295
Weights of Mercur? Deposited on and Evaporated from Samples
sample
So.
sam- - Hg, AIg.
Hg, l f g . Deposited Evap.
Diiference
-0.3 -0.1 -0.1 0 0 .I 0 0 0 2 0 0
0 -0.7 -0.3 0
0 0 -0 4 0 .5 0 .3 -0 1 0
-0.1 0
-0.8 -0.5 -0.4 -0.2 0 -0 1
-0.2 -0.4 -0.1
-0.5 0
O R
0.1 0 -0.3 0
-0.2 0.1 0 -0 6 0
-0.3 0 0.2 0.2
0.1 -0 6
such that the liquid level wa5 above the spherical portion of the flask. Every 5 or 10 minutes the flask was gently agitated. hfter being immersed in the oil bath for 30 t o 35 minutes, the flask was allowed to cool in air to room temperature while the vacuum was maintained. The samples were then individually reweighed to the nearest 0.1 nig., and the weight of mercury lost from each sample was thrn determined by difference. These data are presented in Table I. T h a t the weight loss suffered on heating Tyas due predominantly to the evapointion of mercury was indicated by the follorving experiment: Fifteen tinned-copper samples were numbered, v-eighed, and subjected to the above test procedure, including agitation. The maximum change in weight amounted t o 0.2 mg., the average being 0.1 1 mg. RESULTS 4\D DISCUSSIOY
T h e data in Table I indicate that the average difference betneen the weight of mercury depopited per piece (about 2 mg.) and the eight of mercury estimated by this method is & 0.21 mg. This amounts to an error of apprownately IO'%. The
ple So.
Deposited
51 52 23
1.7 1.7 2.0 1.3 1 7 2.0 1.5 1 5 2.0 1.6
5.1
sJ6 .5 7 58 39 bo
61 fi2 fi3
64 65 66
67 68 69 70 71 72 73 74 7.5
1.0
2.0 2 0 2.4 2.3 2 0 2 3 1.9 1.5
Evap. 2 0 2 3 2 0 2 0
1.7 2 2 2.4 "3 2 2 1.7 1 5 2.0 2 1 2.2 2.0 2.2 1.8 1.9 1.6
2.1 2.0 1.2
1.7 2.0
1.9 1.4 2.3
1.9 1 8 2.5
1.4
Difference -0.3 -0.6 0 -0.7 0 -0.2 -0 9 -0.8 -0.2 -0.1 -0.5 0 -0.1
0.2 0.3 -0.2 0 .5 0 -0.1 0.4 0 -0.2 0 -0.4 -0.2
Sampie To. 7ti 77 78 7:) 80 81 82 83 84 8.5 8A
HE, L l g Deposited Evap. 1.5 2.2 2.2 1.8 1.5 2.0 2.2
1.7
2.2 2.2 2.3
1.5
97 98 99 100
2.0 1.4 2.3 2.2 1.9 1.7 2.3 1.7
2.1 2.5 1.7 1.6 2.0 1.7 2.1 2.0 2.0 2.6 2.6 0.8 1.9 2.2 2.3 2.2 1.9 1.7 2.3 1.8
Total
186.3
199.6
si
88 89 $10 ')1 rc2 93 94 95 96
1.4
1.0 2.0 1.7 2.1 1 5 1.9 2.6 2.0 1. o
Difference -0.2 0 0 -0 5 0 -0 1 -0.3 -0 3 -0 6 0 0 0 -0 5 -0 1 0 -0 6 0.2 0 1
-0.8 0 0 0 0 0 -0.1
k20.9
probable error is f 0 19 mg. as computed by standard statistical procedures The total n eight of mercury added, as determined by the sum of the weights of mercury removed, was 0.1996 gram. This checks remarkably the actual 4 eight of mercury used for tumbling. However, the total weight of mercury added, as determined by the sum of the weights of mercury deposited, amounts to 0.1863 gram, indicating an appreciable R eighing error during preparation of samples. Since preparing the samples containing knon n weights of mercury necessitates an additional weighing compared with the test procedure for unknon n samples, the data reported here probably represent an abnormally high error. Larger quantities of mercury could no doubt be estimated more accurately. LITER4TURE CITED
(1) Eschka, A . , Dengler's Polytech. J., 204, 47 (1872). (2) Hallowvny, G . T.,Analyst, 31, 66 (1906). RECEIVED fcr review March 5 , 1954
Accepted September 29, 1954
Colorimetric Determination of Trace Quantities of Boric Acid in Biological Materials W. C. SMITH, JR., A. J. GOUDIE, Johnson
J. N. SIVERTSON Brunswick, N. J.
and
& Johnson Research Center, N e w
In a rapid and accurate method for the determination
of trace quantities of boric acid in small amounts of biological materials such as blood, urine, and animal tissue, organic matter is destroyed by fusion of the sample with lithium carbonate. The fusion mixture is dissolved in hydrochloric acid; then sulfuric acid is added, followed by a solution of carminic acid. The color develops within 5 minutes. Inorganic materials that are normally found in blood, urine, and animal tissue do not appear to interfere appreciably. Using the Beckman DZi spectrophotometer, the method is capable of determining from 2 to 15 y of boron with an accuracy within &I .Or.
I
X' T H E course of evaluating physiological effects of Iioric acid, it was necessary to determine the boric acid content in small samples of biological material (blood, urine, and animal tissue) in concentrations ranging upward from 1.0 p.p,m, (calculated as boron). Previous workers have developed a varic,ty of methods by which boron has been determined in soils, metals, and various organic materials. Most of these procedures n ere based on one of the following techniques: identical pH titrations, fluorescence measurements, spectrographic methods, and co!orimetric procedure#. When the identical p H electrometric procedure of m7ilc0~(16) was attempted in this laboratory, erratic results were obtained as reported by Berger and Truog (2), since the total quantity of boron available for each analysis wa8 usually less than 10 y .
