Determination of 0-Nitrotoluene in Nitrocellulose Powder by the Immersion Refract omet er JOHNA. O'CALLAGHAN AND STANLEY G. COOK,Naval Powder Factory, Indian Head, Md. PROCEDURE
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T BECAME necessary recently in this laboratory to de-
termine accurately the percentage of o-nitrotoluene in a straight nitrocellulose powder. The direct procedure of weighing the nitrotoluene, or determining its volume after extraction by ether, followed by removal of the ether by evaporation, is not possible because of the volatility of the nitrotoluene and the fact that some nitrocellulose is also dissolved during ether extraction of an ether-alcohol colloided powder. Determination of nitro compounds by the Dumas method is time-consuming. The use of the nitrometer for analysis of nitrotoluene (3) is not recommended, because of the difficulty in transferring the nitrotoluene without loss into the nitrometer. Callan and Henderson get accurate results with their modification ( 1 ) of the Knecht-Hibbert method ( 2 ) . The Callan and Henderson method depends upon the reduction of the nitro group to an amino group by means of a titanous salt, followed by titration of excess reducing agent. The reduction is accomplished by boiling under a reflux condenser. Both reduction and titration are carried on in an atmosphere of carbon dioxide. Whatever method is chosen the nitrotoluene must first be separated from the nitrocellulose. This process presents some difficulties, inasmuch as a small amount of nitrocellulose is inevitably carried along with the ether in an ether extraction. The authors used the immersion refractometer for determination of the nitrotoluene. This method is much simpler than the Callan-Henderson method, but can only be used after the nitrotoluene is obtained in a pure state. The method, as finally developed, consists of extraction of the powder with ether, followed by heating the extract in a distillation flask on the water bath to remove all solvents, and then distilling the o-nitrotoluene by steam into a separatory funnel containing pure ether and a small amount of water. The ether, which now carries the o-nitrotoluene, is separated from the water, its volume accurately found, and the refractive index of the solution determined a t 25" C. by an immersion refractometer. By comparison with a curve prepared from known standards, the amount of o-nitrotoluene is obtained directly. APPARATUS AND REAGENTS The Bausch and Lomb immersion refractometer was employed with a constant temperature bath a t 25" C. Prism A was used. A 100-ml. distillation flask, with neck at least 15 cm. long and a side outlet near the top of the neck, was used in the purification of the o-nitrotoluene extract. The ether used to dissolve the o-nitrotoluene was prepared from the ether manufactured in the Naval Powder Factory. After being redistilled, it was washed very thoroughly with water, then allowed to stand several days over calcium carbonate, and finally distilled over calcium chloride and sodium carbonate. It was stored in brown bottles, and kept in the refrigerator. Before being used to prepare the standard samples of o-nitrotoluene, the ether was shaken with water in a separatory funnel, so that it would be in the same condition as the ether in the actual analysis. Thus prepared, this ether gave a reading on the Bausch and Lomb immersion refractometer, using prism A, of 59.0 a t 25" C.
EXTRACTION. Twenty grams of the sliced or crushed powder are extracted with pure ether for approximately 16 hours in a Wiley extractor. All of the o-nitrotoluene is removed from the powder grains by this treatment, the time required depending upon the fineness of the grains. The ether, when the extraction is finished, contains some alcohol and nitrocellulose, in addition to the o-nitrotoluene. TREATMENT OF ETHEREXTRACT. The ether extract is transferred to a 100-ml. distillation flask. This is closed with a stopper, carrying a thermometer, and is connected with another small flask filled with water to provide steam for distillation. The tube from this flask reaches nearly to the bottom of the distillation flask. The latter is heated on a water bath and the vapors of ether and alcohol allowed to go into the air through the side outlet until all the solvents are evaporated, as shown by the sudden rise of the temperature.
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62 66 70 74 78 a2 a6 IMNIRSIQN REFRACTOPXTER RECIDINGS
FIGURE 1. READINGS ON IMMERSION REFRACTOMETER us. PERCENT BY VOLUMEOF ORTHO-NITROTOLUENE OF 1.168 SPECIFIC GRAVITY IN PUREETHYLETHER
No steam is used during this part of the distillation. The stopper of the distillation flask is loosened and the heating continued a minute or two to rid the flask of alcohol vapors. The entire process takes about one hour. A water-cooled condenser is connected by means of a stopper to the side arm of the flask. The condenser is connected by means of an adapter to a 200-ml. separatory funnel containing approximately 30 ml. of pure ether, free from alcohol. About 20 ml. of water are added to the distillation flask, the water bath removed, and the flask closed. The distillation is recommenced, using steam, but not otherwise heating the distillation flask, until all that remains in the flask, other than water, is a small amount of nitrocellulose. The o-nitrotoluene, carried over by the steam, is caught in the separatory funnel and dissolved by the ether. When the distillation, which requires about one hour, is finished, the condenser and connections are washed with pure ether. The
333
ANALYTICAL EDITION
334
Vol. 5 , No. 5
ether is separated from the water and run into a 100-ml. glass- for 16 hours. The ether was then transferred to a distillation stoppered graduate. It is best to shake out the water in the flask and 2 ml. of alcohol and a known weight of o-nitrotoluene separatory funnel with another portion of pure ether. added. The process was then carried out exactly as has been DETERMINATION OF 0-NITROTOLUENE BY REFRACTOMETER. described. The ether containing the o-nitrotoluene is cooled to 25" C. RESULTB SHOWING ACCURACY OF METHOD in a constant temperature bath, and the volume noted. After WEIGHT OF WEIGHT OF determining and checking the refractive index, the percentage 0-NITROTOLUENE 0-NITROTOLUENE ADDED FOUND ERROR by volume of o-nitrotoluene in the ether solution is read Grams Urams % from curve shown in Figure 1. 1.0286 1.0070 '-2.1 The volume of the ether solution of o-nitrotoluene, multi0.8470 0.8344 -1.5 0,8800 0.8661 -1.6 plied by the percentage by volume of o-nitrotoluene, multiplied by 1.168 (specific gravity of o-nitrotoluene), equals the TESTSON ACTUALPOWDER weight of o-nitrotoluene in ether extract from powder. SAMPLE OB POWDER PREPARATION OF CURVE. The curve shown in Figure 1 DETERMINATSONS No. 1 No. 2 No. 3 is made by testing known weights of o-nitrotoluene, specific Final volume of ether solution at 25' C. 44.0 46.0 45.5 and Lomb immersion refractometer gravity 1.168, dissolved in 25 ml. of pure ether, washed with Bausch reading a t 25' C., prism A (scale divisions 0 t o 100, prism A,hover a range of index water, with the immersion refractometer, prism A a t 25" C. 1.3254 t o 1.3664). 69.5 69.2 68.3 The volume of the o-nitrotoluene is calculated in milliliters Pervalues cent o-nitrotoluene corresponding t o above refractometer readings 1.72 1.67 1.68 from the weights and specific gravity and plotted on the Volume o-nitrotoluene in cubic centimeters 0.7568 0.7682 0.7644 curve against the refractometer readings as per cent by volume Weight o-nitrotoluene in grams 0.8839 0.8918 0.8928 o-nitrotoluene in powder not correctof ether solution, It would be more convenient for calcula- Peringcent for volatiles 4.42 4.46 4.46 o-nitrotoluene in powder correcting tion to have a definite volume of ether solution, and have the Perforcent volatiles and moisture 4.58 4.62 4.62 graph give directly the weight of nitrotoluene in the sample. Twenty grams of powder were taken for each test. Total volatiles = The authors found it simpler and perhaps more accurate, 8.07 per cent. powder, when manufactured, was calculated t o contain about 4.50 however, not to adjust the volume of the ether solution ob- perThe cent o-nitrotoluene. tained a t the end of the process. If the other method is preferred, the amount of ether solution can be set a t a definite ACKNOWLEDGMENT figure, say 50 ml., and the graph so adjusted that it will give The authors wish to express their appreciation to Walter W. directly the weight of nitrotoluene corresponding with any Farnum, chief chemist, Kava1 Powder Factory, for helpful refractive index for this volume. suggestions, particularly that the refractometer be used for EFFECT OF ALCOHOL UPON REFRACTOMETER READINGS this method. Even as small an amount as 1 per cent of alcohol by volume LITERATURE CITED in the ether changes the refractive index sufficiently to vitiate (1) Callan and Henderson, J. Soq, Chem. Ind.,41, 157T (1922). results. It is therefore necessary that all the alcohol be com- (2) Knecht, E.,and Hibbert, E., New Reduction Methods in Volumetric Analysis with Additions," Longmans, 1918. pletely removed from the nitrotoluene. ACCURACY OF METHOD Standards were run as follows: 20 grams of nitrocellulose were placed in the Wiley extractor and extracted with ether
(3) Storm, C. G.,
Orzg.
Com. 8th Intern. Congr. A p p l . Chem., 4, 117
(1912). RECEIVED January 27, 1933. Published with permission of the Bureau of Ordnance, Navy Department.
Determination of Zirconium in Plain Carbon and Alloy Steels THOS.R. CUNNINGHAM AND R. J. PRICE Union Carbide and Carbon Research Laboratories, Inc., Long Island City, N. Y.
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N A PREVIOUS article (1) a method for the determination of zirconium, based on the rapid precipitation of Zr(HPO& in the presence of varying amounts of a number of other elements, has been described. Inasmuch as several workers have experienced some difficulty with the procedure as outlined, and since complete precipitation of the zirconium in the presence of ferric chloride depends upon a rather close control of the acidity of the solution, the following details concerning the decomposition of the sample and the initial separation of zirconium are offered.
PROCEDURE Five or 10 grams (depending upon the amount of zirconium present) of the drillings are transferred to a 600-cc. covered beaker and treated with hydrochloric acid (sp. gr. 1.19), 40 cc. being used for the 5-gram and 60 cc. for the 10-gram sample. The contents of the beaker is heated to 80" to 90" C. until all action appears to have ceased, when from 8 to
15 cc. of Perhydrol (30 per cent hydrogen peroxide) diluted with 25 cc. of water are introduced. The solution is heated for 1 or 2 minutes longer and diluted with warm water to 350 cc. Ammonium hydroxide (1 to 1) is added slowly until a permanent precipitate forms, followed by hydrochloric acid (1 t o 1) dropwise, with stirring, until the precipitate just disappears. From 10 to 20 grams (a sufficient amount to reduce the iron to the ferrous state) of sodium sulfite dissolved in 50 cc. of hot water, and 20 cc. of hydrochloric acid (sp. gr. 1.19) are added in the order named and the contents of the beaker is stirred for 1 minute. Eight grams of diammonium phosphate dissolved in 50 cc. of water are added to the solution of 5 grams of steel or 10 grams to the 10-gram sample. The solution is stirred vigorously for several minutes and the determination completed as described ( 1 ) . The final ZrPzOr precipitate is tested for titanium as follows:
The ignited and weighed precipitate is fused with several grams (a sufficient amount) of sodium carbonate, the melt leached with
