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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.VD ENGI.VEERING C H E - V I S T R Y THE DETERMINATION OF ZINC IN TREATED TIES By FRANCISC. FRARY AND M. GORDON MASTIN Received June 16, 1913
It was recently stated in THISJ O U R N A L t h a t over nine million ties were treated with zinc chloride i n 1911. T h e railroads are said t o be having excellent results with these i n practice, and are buying large quantities of them, mostly on a specification of onehalf pound of zinc chloride per cubic foot, which means about 0 . 5 per cent of metallic zinc. The determination of this small amount of zinc i n such material necessitates t h e use of a rather large sample and t h e complete destruction of t h e organic matter. T h e method commonly used is said t o have originated i n t h e laboratories of t h e Union Pacific Ry., a n d consists in charring t h e sample b y heating with a small amount of concentrated sulfuric acid, and then adding nitric acid, a few drops a t a time, continuing t h e heating until all organic matter is destroyed and nitrous fumes driven off. The solution is then diluted, iron removed, t h e zinc precipitated as sulfide and determined in t h e usual manner as oxide. This method is said t o give satisfactory results with ties except those of oak. Red oak ties in particular are impossible t o analyze b y this method, for t h e treatment with acids, no matter how prolonged, will n o t destroy all t h e organic matter, b u t leaves t h e solution dark colored, and t h e precipitation of t h e zinc is so incomplete t h a t less t h a n half of t h a t present is found. I n some determinations which we made b y this method on t h e red oak shavings used in the work herein described, we found t h a t the zinc sulfide was precipitated in such a finely divided form t h a t i t was not retained b y two thicknesses of C. S. & S. white band No. 589 paper, one thickness of which will retain barium sulfate 2ompletely. This difficulty was brought t o our attention b y hlr. H. M. Newton, of t h e Kettle River Co., t o whom we are indebted for the details of the method of analysis given above and t h e method of Mr. Stenger, described later. We are also indebted t o him and t o t h e Kettle River Co. for furnishing us half of a n untreated red oak tie and another half-tie which had been treated “ t o refusal” with a 4 per cent solution of zinc chloride. The standard method of sampling such material is b y boring with a fine one-inch bit, a t a point two feet from t h e end of the tie. T o obtain a large quantity of material of about t h e fineness of such a sample, we sawed t h e half-tie in two, and reduced half of one of these pieces t o shavings b y means of a shaper in t h e university shop. Similar shavings were taken from t h e untreated half-tie for use with known amounts of zinc. It is a well-known fact t h a t oxalic acid is made b y heating wood shavings or sawdust with caustic alkali, and t h a t care must be taken in t h e process not t o allow t h e temperature t o reach too high a point, or t h e reaction will be too violent and t h e acid will be destroyed. It was believed t h a t it would be possible t o completely destroy t h e organic matter in red oak shavings in this way, and i t was found t h a t such destruction was both easy and rapid if t h e process was
VoI. 5 , No. 9
properly conducted and a little potassium nitrate added toward t h e last. The fusion can not be made satisfactorily in a n iron dish, as some ferrocyanide is usually formed from t h e iron of t h e dish during t h e fusion, and so much iron goes into solution t h a t its separation becomes tedious. By using a nickel dish, very little of t h e metal is dissolved, and t h a t can be easily and quickly removed. The process which has given us t h e best results is as follows: Two grams of t h e dried shavings are weighed into a 200-300 cc. nickel dish, moistened with a little water, and heated gently t o insure thorough saturation with t h e water. Two sticks (about 30 grams) of pure potassium hydroxide are now added, and t h e mixture heated cautiously until t h e hydroxide is melted. The mass must now be stirred thoroughly with a pure nickel wire, and t h e heat increased so t h a t i t boils vigorously. As t h e water is boiled off, t h e fusion becomes almost a salmon-pink (with red oak) a n d lumps of a gummy substance appear on t h e surface. As t h e boiling is continued, these masses disappear, seeming t o dissolve, and t h e color changes t o a yellowish brown. The fusion now begins t o foam a good deal, and must be continually stirred. When spurts of inflammable gases appear, and t h e mass is rather viscous, t h e addition of the nitrate is begun. A piece of potassium nitrate t h e size of a grain of wheat is added, and t h e heating and stirring continued about a minute, repeating t h e addition, heating and stirring as often as may be necessary. The fusion becomes more fluid and lighter in color as t h e nitrate is added. Usually about half a gram of nitrate will be required. When all organic matter is oxidized, the fusion becomes perfectly transparent, colorless, and quiet; t h e dish is then inclined so as t o wash down t h e sides with t h e fused mass and get a n y material t h a t might be lodged there and escape oxidation. After cooling, t h e mass is dissolved in water, 1 5 t o 2 0 cc. of bromine water added, and t h e whole boiled about a minute. T h e nickelic oxide t h u s precipitated is filtered off on a Gooch crucible, and t h e filtrate and washings transferred t o a 7 j o cc. casserole and made barely acid with concentrated hydrochloric acid. Sodium sulfite is added, a little a t a time, until t h e first violent effervescence ceases, and then enough hydrochloric acid added t o make t h e amount of free concentrated acid from 2 t o 6 per cent of t h e final volume. Dilute to about 400 cc., heat t o boiling, and titrate with potassium ferrocyanide, using a saturated solution of uranium nitrate on a spot plate as a n indicator. The conditions for t h e titration are t h e same as for a n y such determination of zinc; the necessary blank must be determined and subtracted from t h e burette reading. For use with a sample of t h e size mentioned, we prefer a solution of about 5 grams potassium ferrocyanide per liter, which is equivalent t o about I mg. of zinc per cc. The blank with such a solution was found t o be about 4 cc., t h e end point being very satisfactory. Enough sulfite must be used t o reduce all oxidizing compounds present, t o prevent them from decom-
Sept., 1913
T H E J@UR?lilL OF I S D U S T R I A L -4.YD E.YGI-YEERIA-G C H E M I S T R Y
posing t h e ferrocyanide, and care should be taken t o keep t h e volume of the solution and its acidity about as above stated. With practice the fusion can be made in about ten minutes and t h e whole determination in half an hour. We prefer t o standardize our solutions with zinc oxide, made by evaporating a little of a solution of c. P. zinc sulfate in a weighed platinum dish, blasting a few minutes t o remove all sulfur compounds, cooling and weighing. The same volume should be used in the standardization as in the regular determination, and about I O grams of ammonium chloride or 40 grams of potassium chloride added t o make t h e conditions t h e same, for it is well known t h a t variations in t h e conditions change t h e value of the ferrocyanide solution. Using this method, on the dried shavings from t h e treated tie, we obtained t h e following results in eight consecutive determinations: 0.881, 0.901, 0.891, o.gog, 0.896, 0.886, 0.901, 0.891 per cent metallic zinc. Using the untreated shavings, and adding t o each determination a solution containing 0.0255 gram of zinc as chloride, t h e following amounts of zinc were found: 0.02j3, 0.0251, 0 . 0 2 j 0 , 0 . 0 2 j 2 , 0.02j3 gram. There is apparently a slight loss of zinc, probably due t o spattering during fusion, being only about 0 . 0 2 per cent b y weight of the original sample of shavings. It is not essential t o the success of this method t h a t t h e zinc be determined b y titration; after removing the nickel and the bromine i t may, of course, be determined b y any other method if desired. S o far as we were able t o determine a t t h e time this work was taken up, the only other satisfactory method for this determination was a n electrolytic one devised by N r . L. A. Stenger, of the Twin City Rapid Transit Co., of this city, and used in their laboratory. hlr. Stenger describes his method as follows: “Five t o I O grams of borings or sawdust are taken, about 150 cc. pure water added, then 6 to 8 grams of sodium hydroxide. The mixture is heated nearly t o boiling for a few minutes, then electrolyzed with a rotating platinum anode and silver-plated copper cathode for about forty minutes. The cathode area is about 2 j 0 sq. cm., and a current of about 5 amperes a t six volts is employed. A tall 400 cc. beaker is used t o allow some space for frothing, which can be prevented by addition of ether if desired. The cathode with the zinc deposit is removed quickly, washed with hot water and alcohol and dried. After weighing, it is replaced in the solution and the electrolysis continued for five t o t e n minutes. If little or no increase in weight is found, deposition is considered complete.” Mr. Stenger very kindly determined zinc in a sample of our dried shavings by the above method, and found 0.88 per cent, which is in good agreement with our results. He also tried our method as above outlined on the same sample, and on tamarack and red oak ties, one of which had been treated with both creosote and zinc chloride, and states t h a t the method worked very well. While we were working on this method, i t was found in the laboratory of the Kettle River Co. t h a t complete
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oxidation of the wood could be obtained, even with red oak, by using potassium chlorate with t h e nitric and sulfuric acids in t h e ordinary method. Mr. Newton very kindly had their laboratory make two determinations on our sample b y this method, t h e results being obtained 0.91 and 0.92 per cent zinc. It is evident t h a t the agreement is as close as could be expected. We believe t h a t this method of fusion with alkali is adapted for the determination of minute amounts of metals in t h e presence of large amounts of organic matter of a n y sort, and have tried it on t h e determination of tin in canned goods, with success. A larger sample can, of course, be used if a larger nickel dish i s a t hand. U N I V E R S I T Y OF
MINNESOTA
MINNEAPOLIS
HICKORY NUTS A N D HICKORY NUT OIL A N D E. H. S . BAILEY Received June 26, 1913
By GEORGE0.P E T E R S O N
Since the hickory n u t crop of t h e United States is a large one, although no accurate statistics exist in regard t o it, it has seemed t o us worth while to make a preliminary study of the properties of the oil. T h e genus carya of the walnut or j u g l a n d a c e a e family comprises eight species, only two of which, t h e carya ovata or shellbark hickory and the c a r y a amara or swamp hickory are here considered. The shellbark nuts are of such commercial value t h a t their oil could hardly be extracted with profit if intended for ordinary table use. The swamp hickory nuts and those called “pig n u t s ” are abundant and a t present not utilized, except as food for hogs and squirrels. Work on t h e composition of nuts has been carried on especially in the Iowa,l California2 and Maine3 -4gricultural Experiment Stations, and from two of these the analyses of hickory nuts (presumably C. ovata) are presented for comparison with our own analysis. TABLEI - C H E M I C A L
HICKORY NUTS P. a n d B. meats 68.0 62.8 30.0 37.2 3.97 3.45 20.5 13.2 64.6 70.2
C O M P O S I T I O K OF
Iowa Sta. Maine Sta. meats Refuse., . . , . , , . , , . Edible portion
62.2(a)
Protein. . . . . . . . . . . . . . . . . . . . Fat.. ........
5.8
Ash ........................ Fuel value per pound in cal-
0.8
ories.
................
..
..
2.2
1.73
1265
3226 (calc.) 2.3 N-free extract.. . . . . . . . . . . . . . . . . . 6.40 ( a ) Per cents in this column refer t o whole nuts.
3310 (calc.) 2.0 9.42
The methods of analysis used were in general those of t h e “ Official and Provisional Methods of Analysis,” Bull. 107, Bur. of Chem., U. S. Dept. of Agr., with such modifications as seemed expedient. All desiccations were carried out in air instead of hydrogen. H I C K O R Y N U T OIL
I n extracting t h e oil from the meats it was decided t o use t h e pressure method rather t h a n t h e extraction 1 “The Chemical Composition of N u t s Used as Food,“ Proc. l a . Acad. Sci., 10, 108-11. 2 “ N u t s a n d Their Use a s Food,” Farmers’ Bull. No. 881. 8 Maine Agr. Erpl. Sla., 1899, 87.
