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T H E J O U 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
THE USE O F TEXTILE FIBERS IN MICROSCOPIC QUALITATIVE CHEMICAL ANALYSIS
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in a dilute aqueous solution of sulfuric acid, washed with water and dried. The transference of the fibers from By E. M. CHAMOTA N D H. I. COLE the hot dye t o the alcohol must be done quickly as Received September 28. 1917 otherwise the turmeric adhering t o the fibers is removed 111-THE DETECTION O F BORON BY M E A N S OF TURMERIC only with difficulty. Too long an immersion in t h e VISCOSE SILK FIBERS1 The reaction of boric acid with turmeric paper, in- alcohol tends t o remove the adsorbed dye as well as the excess dye, volving a color change from yellow t o rose, was first If the fiber still appears t o have any unadsorbed described by Trommsdorff2in 1815. Later investigators turmeric adhering t o it (with viscose silk this is easily showed t h a t this rose color was changed t o blue or noted by the lack of luster) i t can once more be dipped greenish black upon the addition of alkali. in alcohol and washed with water. Any unadsorbed I n this reaction curcumine, the yellowish coloring turmeric interferes with the formation of the blue color matter in the turmeric root, is changed b y the boric acid into another substance, rosocyanine, first described in t h e boron test. This method as given yields a beautiful golden yellow product which was found t o be and named by Schlumberger3 in 1866. I t was so-called eminently satisfactory. by him because of the fact t h a t i t forms rose colored Curcumine of different degrees of purity was also solutions and blue colored metallic salts. Upon tested but since the delicacy of the reaction obtained b y analysis he found t h a t the rosocyanine contained no using the ordinary turmeric extract is exceedingly boron, though the latter was necessary t o bring about great, there is no necessity for other purification t h a n the reaction. t h a t given in the above described method. I v a n ~ w - G a j e w s k i , ~Ciamician and S i l b e ~ - , Milo~ T o determine the influence of the nature of the fiber bedzka,6 and Jackson and Clarke’ have since worked on the delicacy of the reaction, the common textile on this curious and interesting reaction and they found, fibers, flax, cotton, wool, mohair, raw silk, purified as did Schlumberger, t h a t rosocyanine does not contain silk, viscose silk (cellulose xanthate), lustron silk boron. Here, then, is another of those curious chemical (cellulose acetate) and coarse fibers of cupra-amreactions where an element plays a mysterious r61e, monium silk were dyed in turmeric solutions as stated for i t is strangeethat boron alone among the elements above and then used for the boron test. should be able t o induce a molecular rearrangement of Flax, cotton, raw silk, purified silk and viscose silk curcumine into rosocyanine. dyed with turmeric give t h e typical boron test described Emichs suggested t h a t the blue color is due t o a below, while wool, mohair, lustron silk and cuprareaction of cellulose. Jackson and Clarkelg however, ammonium silk more often give a green instead of t h e obtained the blue color when no cellulose was present typical Prussian blue color upon addition of the alkali. and our results as given are in accordance with their Of the various fibers tested, viscose silk gives by far findings. the best color reaction, flax being next best but less I n testing for boric acid in the usual manner with satisfactory in comparison. KOpreliminary treatment turmeric paper, addition of the alkali almost invariably of the viscose silk t o render i t more adsorptive was yields a greenish black color when boron is present found t o be necessary. instead of the much more characteristic blue color. I n Of the various methods tested for applying the applying this test microscopically, however, using inturmeric fiber test for boron, the following procedure dividual fibers instead of strips of paper dyed with gives the most satisfactory results: Place a drop of the turmeric, i t is always possible t o obtain a distinct blue solution of the material t o be tested upon a n object slide color. Having experienced difficulty with flax and and acidulate with dilute hydrochloric acid to decomcotton fibers impregnated with turmeric, i t was thought pose any borates t h a t may be present. I n this drop, worth while t o test out the various controlling factors place a turmeric fiber about 5 mm. long and allow t o for the production of the best and most sensitive fiber. evaporate spontaneously, or by gently warming, t o After various methods of dyeing with turmeric were complete dryness. Cool and examine the fiber under t h e tested, the following one was selected as being the most, microscope. A rose or violet-rose color indicates boron. satisfactory. A 50 per cent alcohalic, alkaline solution To confirm the test, place a drop of a I per cent solution of turmeric is prepared b y boiling approximately 2 0 of sodium hydroxide upon the rose colored fiber. The g. of ground turmeric root with 50 cc. of alcohol and rose color immediately turns t o a beautiful Prussian adding t o the filtered solution a n equal volume of water blue color which gradually changes t o violet. Too high and t o I cc. of dilute sodium hydroxide ( I O per cent). a temperature in the evaporation or failure t o allow The fibers are immersed in this solution which is then the fiber t o go t o complete dryness may lead t o negative evaporated on a water bath t o a syrupy consistency. results. Too concentrated a solution of the alkali will The fibers are rehoved and immediately dipped in 95 interfere with the formation of the blue color. The per cent alcohol, pressed between filter paper, dipped fiber must be observed immediately upon addition of 1 For Parts I and I1 see THIS JOURNAL, 9 (1917), 967. the alkali as the blue color is then most intense. * J . Pharm., 16 (1815). 96. 6 Bull. soc. chim., [ 2 ] 6, (18661, 194. A mineral acid alone with a turmeric fiber on 4 B e y . . 6 (1872). 1103: evaporation t o dryness gives a yellow t o brown color, 5 Gam. chim. ital , 27 (1897), 561. 6 Ber.. 43 (1910), 2163. not the rose or pink color obtained when boron is also 7 Am. Chem. J.. 39 (1908), 696; 46 (1914). 48. present. Furthermore, addition of a drop of alkali 8 Ann., 361 (1907), 429. yields, instead of a blue, a yellow color changing t o the 9 Am. Chem. J., 39 (1908), 696; 46 (19141, 48.
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T H E JOURNAL OF INDUSTRIAL A N D ENGINEERING CHEMISTRY
characteristic mahogany color produced by alkali on the turmeric fiber. It must be remembered t h a t a test for boron as sensitive as this one, must not be performed upon an object slide made from resistance glass containing boron as one of its ingredients. It follows also t h a t apparatus made from such glasses cannot be used for solutions which are t o be tested for the presence of boron. The presence of hygroscopic salts is objectionable, since they prevent the complete drying of the fiber. However, when the solution t o be tested contains more t h a n traces of boron, a satisfactory test may be obtained even in the presence of large amounts of such salts. Any strong bleaching agents, such as hydrogen peroxide or a hypochlorite, must be destroyed before the test can be applied. Much free phosphoric or silicic acid render the detection of boron difficult though not impossible. I n the turmeric paper test for boron as commonly applied, i t has been pointed out t h a t molybdenum, titanium, zirconium, columbium and tantalum may lead to error, because under certain conditions these elements give a color reaction somewhat similar t o t h a t obtained with boron when the alkali is added. This source of error has been carefully studied and we find t h a t the presence of these elements leads t o no misinterpretation of the color changes nor could we obtain with any of these: elements the blue colored fiber, characteristic of boron, when no boron was present. Boric acid can be distinguished from a simple borate in the following manner: Evaporate to dryness without the addition of a mineral acid. A rose-pink indicates boric acid; undecomposed borates yield no rose color. Add the alkali. Eoric acid gives the characteristic blue color, borates do not. Commercial borates of ammonium, sodium, potassium, calcium, barium, iron, lead, nickel, copper and manganese tested as described, gave a boron test from aqueous solutions only afl,er acidification with hydrochloric acid. Ferric borate, however, failed t o give a positive test in very concentrated solution. It milst be remembered t h a t in the presence of inorganic salts which have the power t o decompose a borate, a test for boron may be obtained without the addition of an acid. The c,ensitiveness of this reaction was tested according t o the method already described.l A positive test can be obtained by means of turmeric viscose silk, in one drop of a NI16,ooo solution of boric acid or of a borate, normality being computed with respect t o the amount of boron present. The amount of boron actually present in a drop of a solution of this concentration is o.o00,0%5 mg. SUMMARY
I-Vwose silk, dyed with turmeric, gives a n exceedingiy sensitive microscopic method for the detection of boron in boric acid or in borates. 11-It is possible by this method t o differentiate between boron as boric acid and boron combined as borate, providing substances which will set free boric acid from borates are absent. 1 LOG.
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111-A drop of a solution containing 0.000,025 mg. of boron gives a positive test for boron by this method. IV-
THE DETECTION OF THE HEAVY METALS BY MEANS OF ZINC SULFIDE W O O L FIBERS
The use of fibers impregnated with zinc sulfide, as a microscopic means of detecting t h e heavy metals, was suggested by Emich and Donaul in 1907. They used cotton and guncotton as the carriers for the zinc sulfide. I n making these fibers, according t o their method, we found t h a t it was extremely difficult t o impregnate the fiber with the zinc sulfide. I n order t o overcome this difficulty, we endeavored t o make artificial fibers containing a zinc salt and ultimately t o change this salt t o zinc sulfide, as follows: An ether solution of zinc chloride was mixed with a solution of collodion or “parlodion.” Artificial fibers were then made from this solution by forcing it through a fine capillary opening into a solution of sodium sulfide. The resulting fibers, while sensitive enough, were generally imperfectly formed and the manipulation necessary for their satisfactory production required such a great amount of skill and practice t h a t the method, after many attempts, was abandoned as unreliable. The following modification of this method was also tested. Finely divided and colloidal zinc sulfide was mixed with the collodion and then made into fibers, by extruding into a coagulating‘ liquid, by dry spinning and by making thin films of the mixture and subsequently cutting them. Fibers made by this method also proved unreliable. The common textile fibers were then tested as t o their suitability. Fibers of cotton, true silk, viscose silk, lustron silk, flax, ramie, wool and mohair were immersed in solutions of zinc chloride for several hours, washed with water and placed in solutions of sodium sulfide for z hrs., then washed and dried. Of the fibers treated in this manner, in reagent solutions of different concentrations, wool and mohair alone adsorbed enough zinc sulfide t o give a satisfactory color reaction with the heavy metals. The preliminary treatment of the wool was found t o be important. Fat-free and swelled fibers adsorb more of the zinc sulfide then the untreated fibers. The fat may be removed from the wool by a mixture of alcohol and ether. For swelling the fibers the best results were obtained b y soaking the wool over night a t room temperature in a I per cent solution of sodium hydroxide. This gives the maximum swelling with the minimum detriment t o the fiber. Various zinc salts and methods of impregnating the wool with the salts were tested. It was found t h a t zinc acetate is adsorbed t o a slightly greater extent than either zinc sulfate or zinc chloride. The following method for making zinc sulfide fibers was finally adopted: The defatted wool is swelled by soaking over night a t room temperature, in a I per cent solution of sodium hydroxide. It is then washed and dipped 5 or 6 times alternately in solutions of IO per cent zinc acetate and I O per cent sodium sulfide, pressing out the 1
Ann.. 861 (1907),432.
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excess solution but not washing between dippings. After the final dipping, the impregnated wool is washed a n d dried by pressing between filter paper. Zinc sulfide wool fibers made in this way are sensitive t o 0.001 mg. of copper. The sodium sulfide solution should be freshly prepared b y passing H2S into a solution of NaOH until a portion removed fails t o yield a precipitate with MgC12. The fibers thus prepared are employed as follows: ( a ) Place a drop of t h e solution t o be tested upon a n object slide and add a drop of dilute HC1. Introduce into the drop a zinc sulfide wool fiber about 5 mm. long and examine under the microscope. ( b ) Evaporate t o dryness, add, a drop of dilute ammonium hydroxide, examine the fiber again and introduce into the drop a new fiber t o serve as a means of comparison, in order t h a t slight changes in color may be better discerned. These color changes are yellow, orange, brown or black. I n acid solution the fiber is Straw-yellow.. . . . . . . . . . . . . . . . . . Tin Lemon-yellow. Arsenic, Cadmium O r a n g e , . ...................... Antimony Reddish b r o w n . , Bismuth Byown or yellow-byown. Platinum Copper Mercuric Mercury, Antimdnv fsom'etimes Cobalt. Iron. Manganese, 'Nickel) Black (brown in very dilute solutions.. ...................... Silver, Lead, Gold, Mercurous Mercury
................. ................ ..........
I n acid solution no color, but in alkaline solution the fiber may t u r n b y o w n or yellow-brown if cobalt, iron, manganese or nickel is present. These elements, however, rarely give good reactions with the fibers. It must be remembered t h a t the color of the fiber, as usually observed with transmitted light, varies with the amount of the metal present. For example, a yellow or orange color, if deep enough, may appear brown or even black. On the other hand, an element giving usually a brown or black color with the fiber may color i t a light brown or yellow when only traces of the element are present. SUMMARY
I-A reliable and sensitive method for the preparation of zinc sulfide fibers has been described. 11-Zinc sulfide wool offers a satisfactory test in minute quantities of materials for the presence or absence of metals yielding co1ore.d sulfides. LABORATORY CHEMICAL MICROSCOPY CORNELL UNIVERSITY, ITHACA,N . Y.
A PROXIMATE QUANTITATIVE METHOD FOR THE DETERMINATION OF RUBIDIUM AND CAESIUM IN PLANT ASH B y W. 0. ROBINSON Received November 12, 1917
This method is based on the removal of the major portion of potassium chloride by fractional precipitation with platinic chloride and, further, b y precipitation with strong hydrochloric acid. The resulting solution containing all the rubidium and caesium chlorides and a large amount of potassium chloride is compared spectroscopically with a standard solution according t o the method outlined by Gooch and Phinney. 1
A m , J . Sci., 44 (18921, 392.
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For the determination, 2 0 or more grams of the dry plant are carefully ashed in a muffle where the temperature does not exceed 5 2 5 O C. The ash is dissolved in hydrochloric acid and the excess evaporated off. An excess of freshly slaked lime is added t o precipit a t e the phosphoric acid, magnesium, etc. T h e solution and precipitate are boiled a few minutes and then filtered. The calcium in the filtrate is t h e n precipitated with ammonia and ammonium carbonates and filtered. For the sake of precaution, a second precipitation of the calcium should be made. T h e combined filtrates are evaporated t o dryness, and t h e ammonium salts expelled. This operation must be most carefully done, for the rare earth chlorides a r e extremely volatile. It is best done in a muffle kept just below redness. The remaining alkali chlorides are filtered off with hot water, a few drops of hydrochloric acid added and then about 0.05 g. of platinic chloride. The solution is stirred well and evaporated t o pastiness. Meanwhile a small carbon filter is prepared by drawing out a hard glass tube of l//z in. or less diameter. A perforated platinum foil serves t o hold a small mat of asbestos. The unchanged chlorides of potassium and sodium are rapidly dissolved in the minimum amount of hot water and the chloroplatinates of the rare alkalies with some potassium chloroplatinates washed on t o the asbestos pad with 80 per cent alcohol. Care must be taken not t o use too large an amount of hot water t o dissolve and wash the unchanged chlorides. The platinic chlorides of potassium, rubidium and caesium are then reduced by connecting the carbon filter t o a hydrogen generator and heating gently with a Bunsen burner. The reduction takes place easily, becoming spontaneous when some platinum black is left on the pad from a previous determination and the pad is somewhat moist with alcohol. The chlorides of t h e alkalies are washed through the filter with hot water, the filtrate evaporated t o pastiness in a very small, lipped, platinum dish. The mass is then taken up with four drops of strong hydrochloric acid and filtered through a tiny filter into a vial of about 2 t o 3 cc. capacity. A number of these vials are graduated t o hold the same volume. The rare alkali chlorides are taken up and filtered with two more portions of acid of four drops each, each successive portion being blown through the filter. The solution is made u p t o volume and is ready for comparison. Standards are made u p by treating known amounts of caesium and rubidium chlorides and a n excess of potassium chlorides with strong hydrochloric acid as above. A Bunsen burner is used for the source of heat and i t must be carefully screened from the observer. The chlorides are so volatile t h a t the flame lasts only a few moments. Caesium is identified by the doublets 4 2 1 5 . 6 and 4 2 0 1 . 9 , and rubidium by the double lines 4 5 9 3 . 3 and 4 5 5 5 . 4 . These lines are difficult t o see, and the observer must remain in the dark room for a t least a n hour before the eyes become sensitive enough. The comparison is made by introducing a coil of platinum wire of sufficient size t o withdraw a very
