August, 1928
INDUSTRIAL Ah'D ENGINEERING CHEMISTRY
It is evident from Table VI11 that coals (a) to (d) are practically non-conductors, whereas coal (e), with 90 per cent of carbon and 6.51 per cent of ash, is conducting. I n order to be assured that the conducting quality does not lie in the character of the ash, the ashes of the coals were analyzed. (Table IX) Iron compounds other than pyrites have little influence on the conductivity. Coal (a),with an ash content of 7.73 per cent, of which 21.95 per cent is iron estimated as ferric oxide, is practically non-conducting. It is evident that increase in resistance k not determined by ash content alone, for it is clearly shown that there is a big difference in resktance of actual coal substance for different anthracites. Conductivity of Scotch Anthracites
Two Scotch anthracites were chosen because of their similarity of composition, and wide difference of conductivity (Table X): ( a ) Hassockrigg Colliery, Virtuewell Seam, Lanarkshire ( b ) Polmaise. Main Coal Seam, Stirlingshire Table X-Conductivity of S c o t c h Anthracites (Dry coal. Standard resistance, 7.76 ohms) VOLATILE FIXED COAL MATTER CARBON ASH RESISTANCE Ohms P e r cenl P e r cenl Per cent 9.66 87.36 2.98 6 X 10' (a) 87.40 5.09 75 7.51 (b)
Coal (a) is similar to the Pennsylvanian coal except for lower ash content, and the resistances are of the same order. Coal ( b ) , however, has a greater ash content than (a),and very slightly more fixed carbon when calculated on the dry ashless basis-viz., (a)90.05 and (b) 92.08 per cent; the resistance is, however, only 75 ohms, as compared with a non-conductor.
865
Comparison of Bituminous Coal and Fusain from Same
Finally, the cell was used to clear up an unexplained anomaly in a previous paper,2 in which a description of a Freeport vein coal shows a greater adsorption value towards carbon dioxide than the fusain taken from it. Accordingly, it is proposed to test whether the resistance of the coal and fusain, respectively, follow the order expected for two such substances. The results are summarized in Table XI. Table XI-Adsorption a n d Resistance of Freeport B i t u m i n o u s Coal a n d of Fusain Prepared f r o m I t (One-gram sample. Standard 7.76 ohms) BITUMINOUS COAL FUSAIN Volume of COz adsorbed at N.T.P., cc. 112 45 Resistance, ohms 4 x 106 362
It is evident that the order of resistances is in keeping with what might be anticipated, but the reverse is true for the adsorption figures. The explanation attempted in the previous paper was that the fusain has a lower activity towards carbon dioxide because (1) of infiltrations of bituminous matter into its pores,2 of condensation of oxidation products previously adsorbed in gaseous form, and (3) of the possibility of its not being fusain. The order of the resistances indicates that it is fusain. It can readily be seen that a cell of the nature described can be used to measure the resistance not only of powdered coal but also of any other conducting powders. Acknowledgment Acknowledgment is due to Howard Eckfeldt, professor of mining engineering, Lehigh University, for constructing the cell described; to J. B. Reynolds, professor of mathematics in Lehigh University, for advice about the mathematical work in the paper; and to H. M. Secretary of Mines in London, Col. G. R. Lane-Fox, for the Scotch anthracites specially obtained and analyzed for this work. 2
Sinkinson and Turner, IND.
END CIIEM.,18, 602
(1926), Table IV.
A New Soluble Starch and an Improved Polarimetric Lintner Method' H. C. Gore T H EFLEISCHMAXN LABORATORIES, 1 5 8 T ~ST. A N D MOTTAvE., NEW
I
N T H E polarimetric method proFosed by the writer2 a 2 per cent solution of Lintner's soluble starch was used, and the range within which fall in polarization followed the Kjeldahl law of proportionality during saccharification was slightly more than 3" V. It was obvious that the accuracy of the method could be greatly improved if this range could be increased. It has been found possible to do this through the use of a special type of soluble starch. This new soluble starch is prepared by treating starch with a 13 per cent hydrochloric acid solution. When its 6 per cent solution is allowed to cool and stand at room temperature, it separates into a mixture of coagulum and a solution of starch which can be separated by filtration, while with other soluble starch the 6 per cent solution cannot be filtered clear. A clear, permanent water-soluble solution , of starch of about 5 per cent concentration can thus readily be prepared. With this comparatively strong starch solution the polarization fall with which Kjeldahl's law is followed was found to be a t least 11.3" V. 1 Presented before the Division of Sugar Chemistry at the 75th Meeting of the American Chemical Society, St. Louis, Mo., April 16 to 19, 1928 2 J Assocn Oficrol Agr. Chem , 7 , 364 (1924).
Y O R K , S.
Y.
Details of a polarimetric method retaining the Lintncr scale have been worked out, which, while approximately as accurate as the methods based on the estimation of reduced copper, is far less tedious and exacting. Preparation of Soluble Starch Solution
One part of potato starch is mixed a t room temperature with 1.5 parts of hydrochloric acid of approximately 13 per cent concentration, prepared by mixing 1 part of strong hydrochloric acid by volume with 2 parts of water, and allowed to stand for 6 days. The starch is then washed with distilled water, suspended in water, and the last traces of acid, which cling persistently to the starch, neutralized with ammonia, The starch is then washed several times by decantation, passed through a fine sieve with water to remove any coarse impurities, collected in a Buchner funnel, and washed in the funnel until the washings are free from chlorides. The starch is then dried in a gentle current of warm air. The yield is about 75 per cent of the starch taken. A 6 per cent solution of the special starch is made up by adding the calculated weight, mixed with a little water, to
8.j6
I N D U S T R I A L A N D ENGINEERING CHEMISTRY
hot water, heating to boiling, cooling, and making up to volume. The solution is allowed to cool and stand overnight or longer. It is then filtered on a folded filter, returning the first turbid runnings to the filter. Filtration is slow, and several hours or overnight is necessary. The starch solution thus prepared, preserved by shaking with a little toluene and keeping in a closed flask, keeps indefinitely substantially unchanged. It sometimes becomes slightly turbid, but this turbidity may be readily removed by filtration. Method I n determining the diastatic activity of an infusion of malt, the p H of the starch solution is adjusted to 4.8 by adding Walpole's acetate buffer (8 cc. of 1 N acetic acid and 12 cc. of 1 N sodium acetate made up to 100 cc. with water) a t the rate of 2 cc. of buffer to each 100 cc. of starch solution. The malt infusion is so prepared that each cubic centimeter represents 50 mg. or a known multiple of 50 mg. The initial polarization is made by mixing 50 cc. of the buffered starch solution with 1 cc. of strong ammonia and 5 cc. of the malt infusion, mixed in a dry flask in the order named. The solution is then filtered if necessary and polarized. Five cubic centimeters of malt infusion a t 21 " C. are placed in a dry flask and 50 cc. of the buffered starch solution, also a t 21' C., added, counting time from the moment when the first of the starch solution reaches the malt infusion. The mixture is then allowed to stand in a water bath a t 21" C. for a time within which the polarization should not decrease more than 11.3" V. (where a 4-dc. tube is used in polarizing). One cubic centimeter of strong ammonia is then added, the
Vol. 20, No. 8
solution filtered, if necessary, and polarized. In filtering, the precautions described by Zerbaq3 consisting of rejecting the first runnings of the filtrates and keeping the funnels covered with watch glasses, should be observed. The two solutions should be polarized a t the same temperature to avoid errors due to the marked effect of temperature on the polarizations. The diastatic power is calculated from the formula, 100 D L =
t X l X c
where L is degrees Lintner, D is the fall in polarization observed due to 250 mg. of sample, t is the time in hours, 1 is the length of tube in decimeters, and c is a constant determined experimentally. c = 4.6. Notes on Method
The clear starch solution, prepared as described above from the soluble starch containing 13.25 per cent of moisture, contained 4.706 grams per 100 cc. It polarized a t 105.3" V. a t 20" C. in a 4-dc. tube, and a 25-cc. portion reduced 66.6 mg. of cuprous oxide when treated by the Munson and Walker method. Thus the specifk rotation was 194 and the reducing power expressed as per cent of dextrose was 2.43. The factor c was determined by the use of an infusion of malt, the diastatic activity of which was determined by the gravimetric Lintner method, The soluble starch used in this determination was of Kahlbaum's make, carefully rewashed and redried. The 2 per cent starch solution contained the Walpole 4.8 acetate buffer a t the rate of 2 cc. per 100 cc. of starch solution. 8
Hardin and Zerban, IND. END. CHBM.,16, 1175 (1926).
Electrochemical Polarization Process for Prevention of Corrosion in Locomotive Boilers',' L. 0. Gunderson3 THECHICAGO AND ALTON RAILROAD COMPANY, BLOOMINGTON, ILL.
HE normal life of a locomotive fire box and boiler shell used in a soft or treated non-corrosive water district mag be indefinitJe, while the flues, by successive piecewelding and cutting down to fit shorter boilers, will last upwards of ten years or until worn thin from the fire side. Under these conditions general overhauling of the boiler is made necessary only by federal requirement in interest of safety once in four years, unless an official extension is granted. This overhauling consists of removing and reapplying the flues, examining and renewing n few stay bolts, anti other minor repairs, and generally costs only a few hundred dollars. In a corrosive-water district we may find that fire boxes will last only a comparatively few years, in some localities oiily two or three years, representing a loss of from $2000 to 53000 depending on the size of the locomotmire. During this period the locomotive in such corrosive-water district will have had two sets of flues destroyed by pitting and
T
1 Presented before the Division of Water. Sewage, and Sanitation Chemistry at the 75th Meeting of the American Chemical Society, St. Louis, M o . , April 16 t o 19. 1928. 2 Some details of this process have been noted by the author, Ry. Rev., September 24, 1926; Proc. Pittsburgh Ry.Club, April 28, 1927; A m . RY. Eng. A s m c n . Bull., 29, 135 (1927); Proc. Western K y . Club, March 19, 1928; and by Carrick, J . A m . Water Works Assocn., 19, 704 (1928). 8 Present position, chemical engineer, Electro-Chemical Engineering Corporation, Chicabo, Ill.
grooving, representing an approximate loss of $1200 to $3200 for the two sets of steel flues, in addition to the loss of a few hundred dollars due to scrapping flue sheets and stay bolts that would be destroyed by corrosion. Recently the writer had a close check made of the cost of renewing the belly of a Pacific type passenger locomotive, made necessary because of corrosion in form of grooves and pits after only four years' service. The cost of labor and material was $2150, which included stripping the boiler aud removing it from the frame, all made necessary by corrosion, although the actual cost of the corroded material was less than a hundred dollars. These figures demonstrate the involved character of corrosion in locomotive boilers, where the actual loss is only fractionally represented by the cost of the material. It has been estimated that the railroads of the United States spend 12 to 15 million dollars annually to repair boiler material destroyed by corrosion. To make a correct diagr,osis of cases of corrosion in locomotive boilers is no simple matter, especially on road engines that use a large variety of feed waters on a division. This and other variables make locomotive boiler corrosion a problem much more involved than corrosion in stationary powerplant boilers. In the same water district some boilers will pit and groove primarily a t the forward end, where feed water is injected wit,h more or less oxygen content, and the fire-box end will
