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
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excess solution but not washing between dippings. After the final dipping, t h e 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. T h e 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 t h u s prepared are employed as follows: ( a ) Place a drop of t h e solution t o be tested upon a n object slide and a d d 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 t h e 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
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I n acid solution no color, b u t in alkaline solution t h e 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 t h e fiber, as usually observed with transmitted light, varies with t h e amount of t h e metal present. For example, a yellow or orange color, if deep enough, may appear brown or even black. On t h e 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 t h e 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 a n d Phinney. 1
A m , J . Sci., 44 (18921, 392.
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For t h e determination, 2 0 or more grams of t h e d r y plant are carefully ashed in a muffle where t h e temperature does not exceed 5 2 5 O C. The ash is dissolved in hydrochloric acid and t h e excess evaporated off. An excess of freshly slaked lime is added t o precipit a t e t h e phosphoric acid, magnesium, etc. T h e solution and precipitate are boiled a few minutes a n d then filtered. T h e calcium in t h e filtrate is t h e n precipitated with ammonia and ammonium carbonates a n d filtered. For the sake of precaution, a second precipitation of t h e 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 t h e rare earth chlorides a r e extremely volatile. It is best done in a muffle kept just below redness. T h e 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. T h e 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 m a t of asbestos. T h e unchanged chlorides of potassium and sodium are rapidly dissolved in t h e minimum amount of hot water a n d t h e chloroplatinates of t h e rare alkalies with some potassium chloroplatinates washed on t o the asbestos pad with 80 per cent alcohol. Care must be t a k e n not t o use too large an amount of hot water t o dissolve and wash the unchanged chlorides. T h e platinic chlorides of potassium, rubidium and caesium are then reduced by connecting t h e 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 t h e pad from a previous determination and t h e pad is somewhat moist with alcohol. The chlorides of t h e alkalies are washed through the filter with hot water, t h e filtrate evaporated t o pastiness in a very small, lipped, platinum dish. T h e 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 t h e 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 t h e 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 t h e source of heat and i t must be carefully screened from the observer. The chlorides are so volatile t h a t t h e flame lasts only a few moments. Caesium is identified by t h e 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 t h e observer must remain in t h e 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
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
Jan., 1918
large dr0p.l T h e coil is carefully dried high above t h e flame or on a radiator, taking care t o avoid spattering. The unknown solution is matched with standards b y means of t h e brilliancy of t h e line. An accuracy of from 5 t o I O per cent is easily obtained b y different observers. BUREAUO F SOILS WAhHINGTON, D. c.
T h e following examples will explain t h e calculation required for adopting t h e Sachs-LeDocte or Kruger sugar pipettes t o lime cake analysis: A Sachs-LeDocte pipette delivers 1 7 7 cc. of lead solution and uses a normal weight of 26 g. Therefore, 2 0 0 cc. of solution must be added t o t h e dry matter of t h e lime cake, and if it is assumed t h a t t h e cake contains jo per cent moisture, we have 13 IO 177 = 2 0 0 cc. As it is necessary t o add acetic acid or ammonium nitrate t o decompose saccharates, t h e strength of acid is so adjusted t h a t I O cc. are required. When t h e filtered sample is polarized in a 2 0 0 mm. t u b e twice t h e scale reading is t h e per cent sugar in t h e cake. With t h e Kruger automatic pipette t h e normal weight is adjusted t o t h e size of t h e pipette; for instance, if t h e pipette delivers 123.6 cc., t h e normal weight is 41. 2 g. for beets, and t h e same weight is used for lime cake. T h e amount of solution t o add t o t h e dry matter of t h e lime cake is 158. 5 cc., and if t h e lime cake contains approximately j o per cent of moisture t h e solution is made up of 20.6 14.3 123.6 = I 5 8 . 5 cc. Here 1 4 . 3 cc. of acetic acid solution are used, and t h e polarization in a 200-mm. t u b e is t h e per cent sugar in t h e cake. If t h e moisture content of t h e cake varies appreciably from jo per cent t h e volume of acetic solution added is adjusted accordingly. When “free” sugar is t o be determined, water is added instead of acetic acid. By t h e use of normal lead acetate solution in t h e place of subacetate solution, no acetic acid need be added, b u t in t h a t instance a different weight of lime cake should be used in order t o give t h e proper dilution.
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A QUICK M E T H O D FOR L I M E CAKE ANALYSIS By ALFREDN. CLARK Received November 5 , 1917
The usual procedure in lime cake analysis has been t o weigh out 50 g. of t h e sample in a sugar weighing dish, add acetic acid, mix t o a thin m u d in t h e weighing di3h, transfer t h e contents t o a 200-cc. flask, add lead subacetate solution, and fill t o t h e mark with water. All t h e textbooks describe a method similar t o t h e above, and in which a flask is used. Such a procedure has four serious drawbacks which are avoided in t h e method described below. With t h e flask method, lime is liable t o foam over t h e sides of t h e sugar dish when acid is added; it is difficult t o thoroughly mix in such a small dish without spilling; there is danger of spilling when transferring from the weighing dish t o t h e flask; and thewhole procedure is a slow,disagreeable one. The: writer weighs t h e sample of lime cake i n a counterbalanced, nickel-plated, copper beaker of about 300 cc. capacity, adds t h e calculated volume of acetic acid solution from a pipette, mixes with a small pestle, adds a charge of lead subacetate solution from a Sachs-LeDocte or a Kruger pipette, again mixes with a pestle, and pours onto a filter. T h e dish is large enough t o avoid foaming over, and t h e mixture is not transferred from t h e weighing dish until ready t o filter. 1
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A No. 27 wire B. & S. gauge, coiled seven times around a s/sr rod,
makes a good coil.
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900 N. WASHINGTON AVENUE LANSING, MICHIGAN
I RECOVERY OF LIGHT OILS AND REFINING OF TOLUOL 1 ~~~
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Report prepared by t h e Bureau of Standards in response t o numerous inquiries for information regarding recovery of light oils and t h e refining of toluol. This report was submitted to, and revised in accordance with suggestions of the committee, consisting of representatives of t h e Public Service Commissions, municipalities, manufacturers of gas, and makers OF toluol recovery equipment, organized under the chairmanship of Dr. E. B. Rosa of t h e Bureau of Standards at the request of t h e conference which met a t t h e Bureau July 31, August 1 a n d 2 , 1917. PART I-THE TECHNICAL RELATION OF T H E QAS I N D U S T R Y T O T H E M I L I T A R Y NEEDS OF T H E NATION
usually been considered profitable. Even now, althou8.h several months have elapsed since the United States entered the war, I . HIGH EXPLOSIVES MANUFACTURED FROM GAS BY-PRODUCTS- comparatively few city plants are equipped to recover these The importance of high explosives in the present war has been materials, but the prospects are that in the near future they amply demonstrated. While nearly all kinds of explosives are must do so if the requirements for high explosives are as great used in some way, those which are most in favor for filling as is anticipated. Major Burns of the Ordnance Department high explosive shells are manufactured from benzol and toluol, at the conference held at the Bureau of Standards on August I which substances have their most important commercial stated that the Army is dependent upon toluol for the manusource in manufactured gas of one kind or another. The gas facture of T. N. T. for shell filler. The amount of toluol needed industry thus becomes directly and vitally connected with the depends upon the number of men engaged and how engaged. conduct of the war and a survey of the demands which will be The present estimates are that toluol for shell filler will be made upon it, and its preparedness in a technical way to meet needed in the coming year for our own army, for the allies, and the navy at a rate considerably in excess of the present or these demands, is very important at the present time. anticipated supplies from works under construction. There is 2. CITY GAS PLANTS MUST SUPPLEMENT COKE-OVEN PRODUCat the present time about 4 million pounds per month of T. N. T. niTroru--The constituents of illuminating and fuel gas which are trating capacity and sufficienttoluol is not now available to utilize important in the manufacture of explosives a t the present time it; it is therefore now impossible to place more orders for T. N. T. are benzol and toluol, especially the latter. The removal of primarily because more toluol is not available. It is probable these constituents from the gas which is a by-product of coke- that any and all explosives including the picrates will be necesoven plants has been practiced for some time. Plants manu- sary eventually. facturing city gas, however, have not generally removed these substances from the gas since they contribute to its light- and 3 . MRNTJFACTURINO PROCESSES I N USE I N THE UNITED STATES heat-giving qualities and the substitution of other substances -The manufactured gas distributed in the United States is of t o maintain the gas quality up to prescribed standards has not three principal kinds: Coal gas, carbureted water gas, and oil gas.
