INDUSTRIAL A N D ENGINEERING CHEMISTRY
280
VOl. 15. No. 3
T h e Analysis of TNT-Tetryl Mixtures'.' By C. A. Taylor and Wm. H. Rinkenbach PITTSBURGH EXPERIMENT STATION,BUREAUOF MIXES, PITTSBURGH, PA.
IXTURES of T X T ( 2 :4:6 trinitrotoluene) and tetryl ( 2 :4:6 trinitrophenylinethylnitramine) have been in use in the explosives industry for some time, particularly in the manufacture of detonating fuses. The usual method of analysis has been to determine the nitrogen content by the Dumas method and to calculate the relative percentages from this. This method is subject to error and is tedious. The writers recently made a study of the binary system TNT-tetryl, deriving an equilibrium curve for this mixture. A molecular compound was found to be formed, and directions for the use of this curve in the analysis of unknown mixtures were given. As a result of work done in this laboratory on the solubility of T N T and of tetryl in organic solvents, it has been found possible to work out a new method of analysis of mixtures of these substances. DERIVATION OF METHOD The studies of the solubilities of these two substances in a number of organic solvents showed the greatest value for the solubility of T N T a t a definite temperasolubility quotient solubility of tetryl ture when carbon tetrachloride was used as the solvent. With this solvent, the value of this quotient increases with increase in temperature; but it was decided to make the determinations a t 0" C., as this temperature can be maintained without the use of the thermostat, filtrations can be made without difficulty, and T N T is at this temperature about thirty times as soluble as tetryl. The solubility determinations had shown that 100 g. of carbon tetrachloride would hold in solution 0.215 g. of T N T a t 0.3" C., or 0.0073 g. of tetryl a t 0.5 C. I n order to use a volume of about 100 cc. of carbon tetrachloride, sp. gr. 1.629, the weight of sample was fixed a t 0.35 g. so that if the T N T was pure it would all go into solution. METHOD Thirty-five hundredths of a gram of the dry, well-ground sample are weighed and washed with pure carbon tetrachloride into a previously dried and weighed 100-cc. volumetric flask having a short neck and a ground-glass stopper. The volume of carbon tetrachloride is made up to about 100 cc., and the mixture is heated to boiling in order to insure the solution of all T N T present. The flask is stoppered and is allowed to cool to room temperature, and weighed. The bulb of the flask is now immersed in an ice bath for 4 hrs., the contents being agitated every 15 min. or half hour. At the end of this time, a sample of the supernatant solution, which should be between 0" C. and 0.5" C., is taken. The sample should be as large as possible and may be taken by means of a weighed wagon-pipet, as described in detail in the articles on solubility of T N T and tetryls3 If this hype of solubility tube is not available, the method may be modified with but little resulting error, thus: A short piece of rubber tube holding a cotton filter-plug is attached to the tip of a 100-cc. pipet, a sample is quickly drawn into the tube and this is immediately transferred to a pre-
-
Received September 21, 1922. Published by permission of the Director, U. S. Bureau of Mines. a J . Am. Chem. S O L , 46 (1923),44, 104. 1 2
viously dried and weighed Erlenmeyer flask having a tightfitting stopper. After bringing to room temperature, the flask and sample are weighed and the carbon tetrachloride is evaporated by means of a current of dry air, after which the residue is dried a t 60" C.
INTERPRETATION OF DATA All the T N T present and some of the tetryl will remain in solution a t 0" C., and, on analyzing a weighed sample of this solution, we can calculate the total solids held in solution by the total weight of carbon tetrachloride used. Knowing the solubility of tetryl in carbon tetrachloride at this temperature, the amount dissolved can be calculated and is subtracted from the value for the total dissolved solids found above. This gives the weight of T N T present in the sample, which is calculated to a percentage basis. If A = total weight of CCl4 used, B = weight of CC1, in sample taken, C = weight of residue from sample, the percentage of T N T in the sample can be calculated by use of the formula
-
A (IOOC 0.0073B) = per cent of TNT in sample B X wt. sample
RESULTSOBTAINED Known mixtures of T N T and tetryl were prepared, fused, and thoroughly ground. The fusion was carried out because under these conditions these two substances form a molecular compound, and it was desired t o ascertain whether this would be dissociated by the action of carbon tetrachloride. On carrying out the procedure previously outlined, the following results were obtained, triplicate determinations being made on all but one mixture: Percentage T N T Actually Present
30.0 60.0 80.0
--1 29.94 60.08 82.06
Percentage of T N T Found 2 3
29.88 60.37
.....
30.22 60.61 81.80
Average
30.01 60.32 81.93
From theseZfiguresit would appear that this method affords a fairly rapid and easyimeans of determining the relative percentages present with an accuracy within 2 per cent, the error increasinglwith the percentage of T N T present. While not strictlyvaccurate, it is believed that the method will fill a want, and may be further developed so as to yield more accurate results.
PRECAUTIONS As stated before, the mixture of sample and carbon tetrachloride should be brought just to the boiling point and cooled before weighing, in order to insure complete solution of all T N T present. The solution should be immersed in the ice bath for 4 hrs. in order to insure precipitation of all possible tetryl, as this substance shows an appreciable lag in attaining equilibrium. When cooled to 0" C. and maintained there for only 1 hr., the following results were obtained: Percentage T N T Actually Present 60.0
-Percentage of TNT Found65.00 61.61 60.51
On withdrawing the sample by means of the wagon-pipet the tube and contents should be left under a partial vacuum
March, 1923
INDUSTRIAL A N D ENGINEERING CHEMISTRY
in order to permit expansion with increase of the temperature to that of the atmosphere. A temperature higher than 60' C. should not be used for the final drying of the residue in the tube or Erlenmeyer flask, as tests have shown that above this temperature an appreciable amount of T N T is volatilized in a short time. Drying should be continued to constant weight, but experience has shown that under the above conditions this is attained within the 2 hrs. stated.
281
The temperature of the solution during immersion should always be lowered to 0" C., or to within a few tenths-of a degree of that temperature. On cooling to only 2.5" C., the following results were obtained: Percentage TNT Actually Present
60.0
--Percentage
60.83
of T N T Found-os 58.71
59,
T h e Effect of Certain Chemicals upon t h e Filtration of Ripe Imhoff Sludge19z By P. A. van der Meulen3 and R. 0. Smith4 RUTGERSCOLLEGE
AND
THE STATEUNIVERSITY O F NEW.JERSEY,N E W BRUNSWICK, h'. J
The e&ct of certain chemicals, especially sulfuric acid, sulfurous acid, and aluminium sulfate, on the filterability of ripe lmhoff sludge has been studied. The addition of relatively small quantities of sulfuric acid in increasing amount results at first in a more gelatinous cake, then gives a sharply defined point at which the cake becomes less gelatinous, and is filtered more readily. A further increase causes the cake to become gelatinous again. The acidity of the filtrate f r o m this optimum treatment corresponds to a pH value of 4.2. The odor of the filter cakes is offensive. The action of su!furous acid appears to be similar to that of sulfuric acid, but a larger amount is required to produce the same effect.
The addition of gradually increasing, small amounts of aluminium sulfate gives a cake that is very porous and one that is rapidly freed of visible moisture. There is no reversal to a gelatinous cake with increasing amounts of the reagent within the range studied, as in the case of sulfuric acid. The odor of the cakes is not ogensive. By using a cloth filter unit of the laboratory type, the weight of cake obtained in a given time is increased more than three-fold by the addition of an amount of aluminium sulfate corresponding to 6.7 Ibs. per cubic yard of the sludge. The further addition of coal ashes gives a somewhat increased weight of cake over the weight of ashes used. The addition of clay and powdered burnt lime has either no appreciable effect, or else has a deleterious one.
T
gas when formed and thus permit more accurate measurement of the portions taken for filtration. Forty-cubic centimeter portions of the treated samples, corresponding to 331/3 cc. of the original sludge, were measured into Buchner funnels fitted with filter papers, and suction from a suction pump was applied simultaneously to the entire connected series. Filtration was continued for 20 min., as that is sufficient time to give significant differences in this case. When a sample was filtered free from visible moisture in less than 20 min., the time was noted. All experiments were carried out a t room temperature (about 23' C.). The filtered solids were then scraped off the filter paper, placed on a weighed watch glass, and weighed a t once and again after drying a t 105" C.
H E TECHNIC developed by Wilson and Heisig6 in their study of the relation between the ease of filtering activated sludge and the pH value of the sludge was of interest in connection with a similar problem attending the disposal of Imhoff sludge at the Plainfield plant, in which the authors are i n t e r e ~ t e d . ~ In preliminary work, portions of ripe Imhoff sludge were treated with varying amounts of solutions of sulfuric acid, sodium chloride and sulfate, calcium chloride, ferrous sulfate, and aluminium sulfate and chloride, and the resulting mixtures filtered with suction. The results obtained indicated that sulfuric acid and aluminium salts gave quicker and more complete separation of liquid from solids than any of the other solutions. For further study and comparison 100-cc. portions of ripe Imhoff sludge were treated with varying amounts of N sulfuric acid or N aluminium sulfate [lo0 g. Alz(SO& (17 per cent Al203) per liter], diluted before addition to the sludge to 20 cc. with water, except in the case of the control when this volume of water alone was added. This gives a total volume of 120 cc. in each case. The treated samples were shaken well, to assist in the evolution of 1 Presented before the Division of Water Sewage and Sanitation at the 64th Meeting of the American Chemical Society, Pittsburgh, Pa., September 4 to 8, 1922. * Paper No. 108 of the Journal Series, New Jersey Agricultural Experiment Stations, Department of Entomology. This paper will appear in Rutgers College Studies, Vol. 1. 8 Associate Professor of Chemistry, Rutgers College and The State University of New Jersey. 4 Sewage Specialist, New Jersey Agricultural Experiment Station and the New Jersey Department of Health. 8 THIS JOURNAL, 18 (1921),406. 6 See also Hatfield, "The Fertilizer Value of Activated Sludge," Illinois State Waler Survey, Bull. 16 (1918-1919), 129.
EFFECT OF DIFFERENTTREATMENT ON MOISTURE CONTENT The per cent moisture found in the filter cake against cubic centimeters of normal acid, for the average of four series of experiments, and similarly for seven series when normal alum was used on ripe Imhoff sludges secured from July, 1921, to March, 1922, are plotted in the accompanying figure (page 282). With increasing amounts of acid there is a uniform rise in €he moisture content of the filter cake, followed by a decrease in the moisture content to a very sharp minimum. Any variation on either side of the optimum treatment gives a decided increase in the moisture content and a more gelatinous cake. The shortest time for any sludge to filter free from visible moisture was 15 min. corresponding to the above minimum, and all other acid-treated sludges were not free from visible moisture in 20 min. The pH value of the filtrate from the controls was between 8.2 and 8.4, while that corresponding to the sharp minimum averaged 4.2. The filter cakes
