T H E J O V R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
5 76
The cellulose residues obtained by various alkali treatments differ apparently in their physical nature, a n d further chemical investigation is necessary. Such researches will be made shortly by t h e author. LIGNIN-Konigl treated t h e extracted lignified materials with 7 2 per cent sulfuric acid according t o t h e method of Ost and Wilkening,z and regarded t h e noncellulose residue as lignin. This method was recently applied by Dore for the determination of lignin in wood. The d a t a for lignin in hemp and ramie given i n this paper were obtained b y Konig's method. b The lignin, which is believed b y investigators t o exist in combination with cellulose as lignocellulose, may not be a constituent of t h e bast fibers belonging t h e pectocellulose proper. The cuticular tissue of fibers in t h e stem, which is much lignified, occurs in intimate contact with t h e bast fiber and part of i t remains after t h e scutching operation. It appears t o t h e author t h a t t h e determination of lignin in hemp a n d ramie serves as one of the indications of t h e completeness of the whole retting process. The lignin is partly attacked b y alkali digestion, and experiments were made on t h e effects of such digestion upon t h e yield of lignin. Two grams of t h e fibers were dried, extracted with benzene, alcohol, water, and one per cent sodium hydroxide as in t h e cellulose determination., and t h e lignin determination was made upon t h e dried residue as before. The results are given in Table IV. TABLE IV-EFFECT
OF
ALKALIDIGESTION O N THE YIELD OF LIGNIN HEMP RAMIE
Loss on drying.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Benzene extract., . . , . , , , , . , , , , , , , . , , . . , , , , , .
,
8.83 1.92
. . . . . . . . . . 1.20 . . . . . . . . . . 4.50 e . . . . . . . . . . 18.53 Cellulose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62.42 Lignin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.99 TOTAL. .......
......
--
99.39
10.50 0.86
0.75
3.79 17.27 65.88 0.18
-_
99.23
SUMMARY
I-The proximate compositions of Korean hemp and ramie are given, as determined by modifications of t h e analytical method proposed by Dore. 2-The analytical results are discussed from t h e textile chemistry standpoint for the benefit of future investigations. 3-The presence of lignin in both hemp and ramie is confirmed quantitatively. My sincere thanks are given t o Mr. W. H. Dore for his kind suggestions and encouragement. SHORT COMMERCIAL ANALYTICAL METHODS FOR THE DETERMINATION OF PURITY OF IMPORTANT CHEMICALS USED IN PYROTECHNICS By Henry B. Faber and William B. Stoddard NEWYORE,N. Y. Received January 29, 1920 1-DETERMINATIOS
OF
SMALL
AMOUNTS
OF
I n potassium nitrate t o be used in t h e manufacture of military pyrotechnics, t h e presence of salts of sodium is t o be avoided for two reasons: 2
Chem.-Zlg., 36 (1912), 1101. I b i d . , 34 (1910), 461.
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No. 6
I-On account of t h e flame color imparted b y small amounts of sodium compounds. 2-On account of t h e hygroscopicity of sodium nitrate, which might cause the finished articles t o absorb moisture t o such a n extent as t o irtterfere with their proper functioning. The problem, therefore, became one of determining sodium nitrate in quantities as low as 0.01 per cent in potassium nitrate. Reference t o t h e literature indicated t h a t t h e method of Walter Craven Ball' was t h e only one available. This method is based upon t h e fact t h a t when a solution of potassium nitrate, bismuth nitrate, a n d cesium nitrate, acidified with dilute nitric acid, is added t o solutions of sodium nitrate, even in t h e presence of large quantities of potassium salts, t h e sodium is quantitatively precipitated as cesium sodium bismuth nitrite, having t h e formula 5 Bi ( N02)3.gCsN02.6NaN02. The precipitate is obtained in t h e form of large yellow crystals which are very easy t o handle. It was found convenient t o modify t h e method used b y Ball, who made t h e precipitation in a separatory funnel, t h e upper part of which was kept filled with coal gas. After t h e precipitate had entirely separated, i t was removed b y poking t h e crystals down through t h e stopper of the funnel. The present writer has found t h a t a series of 3 0 cc. Erlenmeyer flasks can be used for making a number of determinations a t t h e same time. One gram of each sample of potassium nitrate t o be analyzed is dissolved in 5 cc. or less of water and placed in a flask. One cc. of 2 N nitric acid is then added and, by means of a pipette, I O cc. of t h e reagent. The flasks are shaken and connected, and coal gas is passed through t h e series until t h e air has been replaced. The rubber t u b e a t one end of t h e series is then closed b y a glass plug, and t h e other end b y a Bunsen valve, which is used in order t o permit t h e escape of nitrous fumes which are developed in small amount. T h e cesium sodium bismuth nitrite begins t o separate within a few minutes and collects on t h e bottom of t h e flasks as a yellow crystalline precipitate. The flasks should now be allowed t o stand i n a cool place for 48 hrs., during which time no scum should appear on the surface. The stopper is removed, and t h e flask rotated t o loosen t h e precipitate from t h e glass, tilted t o an angle insufficient for t h e liquid t o run out. and t h e neck placed against a n asbestos pad in a Gooch crucible.2 The crucible, with t h e flask, is rapidly righted. The flask is now in a n inverted position, t h e neck resting on t h e asbestos pad. I n this position t h e flask and crucible are rotated with a slight vertical motion t o wash all t h e precipitate from t h e bottom of t h e flask. The flask is then slowly raised, permitting t h e solution t o enter t h e crucible, a n d t h e neck carefully withdrawn with a slight rotary
SODIUM
I N THE P R E S E N C E O F L A R G E A M O U N T S O F P O T A S S I U M
1
Vol.
Full details as t o 1 J . Chem. SOL, 96 (1909), 2126; 97 (1910), 1448. the preparation of the reagent, and the technique and accuracy of the method are given in the second paper. 8 This pad, which should fill one-third of the crucible, is prepared in the usual manner and finally washed with 10 cc. of 50 per cent acetone followed by 15 cc. of pure acetone in three portioas, each portion being removed separately by suction. The crucible is then dried in an air bath a t 100' for 30 min. and weighed.
June, 1920
T H E JOURNAL OF INDUSTRIAL A N D ENGINEERING CHEMISTRY
motion t o remove any adhering particles of t h e precipitate or asbestos. The thickness of t h e asbestos pad is sufficient t o prevent any of t h e solution from going through it until t h e crucible has been placed in a suction funnel. Suction is applied rapidly until three-fourths of t h e solution are passed through the crucible, when it is released. A small amount of t h e filtered solution is returned t o t h e flask and a "policeman" used t o remove any part of t h e precipitate t h a t may have adhered t o t h e glass. The liquid is then transferred t o t h e crucible and suction again applied. The solution is rapidly filtered and t h e sides of t h e crucible and t h e precipitate are washed with 5 cc. of a 50 per cent acetone solution in a very fine stream. Suction is applied until t h e solution is passed through, and 1 5 cc. of pure acetone are added in 3 portions, each portion being passed through t h e filter by suction and t h e suction stopped before t h e next portion is added. T h e filtering operation is t o be as rapid as possible, and a very small filter flask t o be used, t h e object being t o minimize exposure of t h e precipitate t o t h e air in t h e presence of the reagent. Should a small amount of scum appear during t h e second filtration it may be disregarded, as i t has no effect on t h e estimation. T h e filtrates should be perfectly clear before t h e acetone is used. The crucible is then dried i n an air bath at 100' for 30 min., weighed or titrated as later indicated. The weight of t h e precipitate multiplied by 0.03676 will give t h e weight of t h e sodium calculated as metal. V 0 L U M E T R I C D E T E R M I N AT1 0 N
As t h e precipitate is a complex nitrite, it may be titrated b y a standard solution of potassium permanganate, according t o t h e following procedure: * After drying, t h e precipitate with t h e asbestos p a d is transferred from t h e crucible t o a beaker, 1 5 0 cc. of water added, followed by a known volume of a standard solution of approximately 0.1 N potassium permanganate in excess of t h e amount required for the ,oxidation. Forty cc. of sulfuric acid ( I : I ) are added .and t h e solution heated t o 70' C. The excess of potassium permanganate is titrated by means of a standard solution of approximately 0.I N sodium oxalate. The available oxygen of the permanganate consumed under t h e acid conditions, multiplied by 7.820, will equal t h e weight of t h e cesium sodium "bismuth nitrite. Since 30 atoms of oxygen are -required for each molecule of t h e precipitate in order t o convert t h e nitrites t o nitrates, extended tests have established t h e availability of this volumetric method. The cesium may be recovered from the filtrates by %he addition of silver nitrate in slight excess, which precipitates a very insoluble cesium silver bismuth nitrite. This on heating and subsequent extraction with water yields a pure cesium salt. From t h e factor given (0.03676), i t will he seen t h a t I mg. of sodium will produce over 2 7 mg. of precipitate a n d consequently t h e amounts of various materials to be used for analysis must be gauged according t o %heir sodium content. From 3 t o 8 mg. of sodium will
577
be found t o be a very convenient amount t o be used in t h e application of this method. 11-DETERMINATION
O F ALUMINUM I N ALUMINUhl FLAKE OR DUST
As t h e use of finely divided metallic aluminum is essential in modern military pyrotechnic practice where t h e production of intense illuminations is desired, i t is evident t h a t a rapid and easy method for t h e determination of t h e metallic aluminum content of such material is of great value. As the presence of t h e usual small amounts of foreign materials, such as silicon and iron, does not interfere seriously with t h e result, t h e following methods may be more correctly designated as t h e determination of t h e total reducing power of t h e material rather t h a n t h a t of its metallic aluminum content. The literature contains reference t o two methods. One of these depends upon t h e volume of hydrogen which a sample of t h e metallic aluminum will liberate when treated with acid. I n t h e case of flake aluminum this method is difficult t o apply, owing t o t h e fact t h a t the material is so light t h a t most of i t floats. Another method depends upon t h e reduction of ferric sulfate t o ferrous sulfate. The results from this method, however, were not uniform and very unsatisfactory,. due no doubt t o t h e formation of hydrogen during t h e reaction. Attempts were made t o use other oxidizing agents t h a n ferric sulfate, among them silver nitrate and iodine in potassium iodide. The results from these methods were all low, indicating t h a t some hydrogen must have been produced during t h e reaction. After a long series of experiments i t was found t h a t ' t h e reducing power of t h e aluminum dust or flake on litharge, PbO, can be easily determined. I t was found t h a t t h e accuracy depended upon two factors: first, the formation of a liquid slag from which t h e globules of metallic lead could easily separate themselves; and second, the temperature a t which t h e assay was run. It was found convenient t o make these assays in what are known as 25-g. fire-clay crucibles. A charge of 3 g. of metallic aluminum proved t o be an appropriate amount for t h e determination. The aluminum is mixed with I O O g. of litharge and 3 0 g. of borax glass and a cover of 2 j g. of borax glass is added. These proportions yield an amount of slag t h a t is convenient t o handle and of such a nature t h a t it fuses readily t o a very liquid mass, which can be easily and cleanly poured out of t h e crucible. The fusions are conducted in a gas muffle heated t o such a temperature t h a t t h e dividing line between t h e end of t h e muffle and its bottom cannot be distinguished. The fusions require 2 0 min. after the crucibles are placed in t h e preheated muffle. After t h e fusions are complete, t h e molten mass is poured from t h e crucible into a conical slag mold such as is used b y assayers. I n these molds t h e molten lead settles t o t h e bottom. After cooling, the lead bottoms break away easily from t h e slag, which is brittle, slightly yellow, almost transparent, and glassy in character.
T H E J O U R N A L OF I N D U S T R I A L A N D EiVGINEERING C H E M I S T R Y
578
.
Finally t h e lead bottoms are pounded into cubes t o remove any adhering particles of slag and are then weighed. The accuracy of t h e results were found t o depend upon the temperature a t which t h e fusions were made. The requirements are t h a t a high temperature should be used throughout, in order t h a t t h e required time may be short, so as t o minimize t h e reoxidation of t h e lead. According t o t h e equation 2Al 3PbO = AlzO; 3Pb, t h e weight of t h e lead multiplied b y t h e factor 0.0872 will give t h e equivaient weight of aluminum. The following results were obtained' on 3-8. samples of aluminum:
+
+
LSAD
-ALUMINUM--. Grams Per cent 2.9283 97.61 2.9489 98.29 2.9338 97.79 2.9195 97.32 2.9371 97.90 2.9271 97.57 2.9270 97.57
Grams 33.580 33.181 33.645 33.480 33.683 33.568 33.567
I t should be noted t h a t this method permits t h e use of a comparatively great weight of aluminum and further t h a t t h e fact t h a t t h e lead produced weighs nearly 1 2 times as much as the aluminum contributes t o t h e accuracy of t h e results. The method is quick, easy, and accurate from a practical standpoint. 111-DETERMINATION
O F NITRATES SALTS
IN
COMMERCIAL
Vol.
12,
NO. 6.
THE APPLICATION OF THE ROTATING ZINC REDUCTOR IN THE DETERMINATION OF MOLYBDENUM By Walter Scott KENT CHEMICAL LABORATORY, YALE UNIVERSITY, NEWHAVEN,CT. Received January 5, 1920 INTRODUCTION
I n former articles' results have been given showing t h e efficiency and rapidity of rapidly rotating metallic reductors in t h e reduction and determination of vanadic acid and ferric sulfate. I n the present work a similar method has been applied t o molybdic acid. The reduction of molybdic acid b y zinc is well known. Wernke2 carried t h e reduction with zinc and sulfuric Using acid approximately t o t h e condition of MOIZO~Q. t h e Jones reductor, Dudley3 obtained slightly different results, while Jones4 and Doolittle and Eavenson6 obtained results similar t o those of Wernke. Blair and Whitfield,6 and Miller and Frank7 obtained a reduction approximately to t h e condition of Moq403,, while W. A. Noyes and Frohman,8 b y replacing a i r with carbon dioxide, got a degree of reduction corresponding t o MozO3. Randall,Qusing ferric alum in t h e reducing flask and decolorizing with phosphoric acid according t o Reinhardt'O obtained a reduction t o t h e condition of Moz03. REDUCTION O F
MOO3
B Y ROTATING ZINC CYLINDER
I n all t h e following results t h e molybdenum has been estimated as RiloO3, t h e source of molybdenum being At t h e present time t h e nitrates of potassium, ammonium molybdate1' which contained 81.35 p e r barium, and strontium are extensively used in t h e cent Mo 0 3 . manufacture ..of military pyrotechnics. A rapid and Preliminary experiments showed t h a t t h e rate of easy method for t h e determination of t h e pure nitrate content of t h e commercial salts depends upon the fact, reduction at temperatures between 20' and 30' C. t h a t when any of t h e above compounds are heated was nearly as rapid as when started a t t h e boiling with an excess of tungstic anhydride (Woa), oxygen temperature of t h e solution, complete reduction being a n d oxides of nitrogen empirically corresponding t o accomplished in about j min., for t h e amounts of M o o 3 taken. A t temperatures below 2 0 ° C., howN206 are liberated. ever, t h e reduction was much slower. Gooch and Kurzirian' have shown t h a t sodium I n t h e first series of experiments, t h e results of which paratungstate NaIcW12041 has t h e property of decomare shown in Table I, t h e reduction was brought a b o u t posing nitrates. It was found on trial, however, t h a t b y a solid zinc cylinder into which was fixed an i r o n t h e use of tungstic anhydride gave better results owing spindle attached t o t h e shaft of a small motor which t o t h e fact t h a t there was no loss b y spattering during was r u n by t h e ordinary city current. When an elect h e fusion, a loss difficult t o avoid if t h e paratungstate trolytic current was used, i t was obtained from 8 was used. storage cells. This cylinder was used in obtaining all One gram of t h e nitrate is mixed in a platinum cruci1 Gooch and Scott, A m . J . Sci., 46 (1918), 427; Scott, THIS JOURNAL, ble with approximately 5 g. of tungstic anhydride, 1 1 (1919), 1135. prepared by igniting tungstic acid in a platinum 2 Z . anal. Chem., 1 4 (1875), 1 . 8 J . A m . Chem. Soc., 15 (1893), 519. crucible with a good Bunsen burner for an hour, and 4 Am. Inst. M i n . Eng., 18 (1889-go), 705. subsequently kept in a desiccator over sulfuric acid. 6 J . Am Chem. Soc., 16 (1894), 234. The mixture is heated carefully over a Bunsen burner, 6 I b z d . , 17 (1895), 747. 7 I b i d . , 26 (1903), 919. finally using t h e full heat of t h e flame. The reaction 8 I b i d . , 16 (1894). 553. is generally complete within I O min. From t h e loss 9 A m . J . Sci., [41 24 (19071, 313. 10 Chem.-Ztg., l a (1889), 323. in weight t h e percentage of t h e pure compound in the 1 1 Treadwell-Hall (3rd Ed. (1911), p, 284) states that molybdenum commercial sample is easily calculated. trioxide may be obtained from ammonium molybdate b y heating carefully This method was tested with carefully purified in a spacious crucible, finally t o dull redness. The writer found that a t very low redness a small amount of molybdenum trioxide always subsamples of potassium nitrate, barium nitrate, and limed. This sublimation was overcome by thoroughly mixing the ammostrontium nitrate, yielding results within 0.0j per cent nium molybdate with 5 or 6 times its weight of acid tungstate of sodium, applying heat gently at first and finally t o low redness. The anhydrous of t h e theoretical in each case. 1
A m . J . Sci., [41 81 (1911), 497.
acid tungstate .was prepared b y adding tungstic trioxide to fused sodium tungstate. The composition of the tungstate was practically NaaWzO7 or NaaO.2WOs.
