June, 1913
T H E JOUR.\-AL
OF I.YDrSTRI*-lL A.YD E?\-GI*YEERISGCHEMISTRY
of the acid removed; in favor of stopping we have the cost of continuing and the cost of refining the distillate. Both of these costs include not only the steam required but the capacity of the apparatus as well, so that a rather complex computation is required t o settle the point. Prodncts Lost in the Gas.-The non-condensable gas which escapes from the retort condensers carries with it a certain proportion of vapor of pyroligneous acid. The proportion of this vapor in the gas depends only on the temperature t o which the products are cooled in the condenser, but even with the best cooling there will still be some vapor lost. As far as the writer knows, this loss of pyroligneous acid is not being prevented a t any plant in this country, although in Europe the use of gas scrubbers for thit purpose is quite common.1 In determining the advisability of installing scrubbers to recover a t least part of the valuable products from the gas, the cost of collecting and washing the gas and of refining the wash water must be balanced
I
against the value of the alcohol and acetic acid saved. The cost of washing the gas and of refining the wash water and the amount of products recovered will vary considerably, depending on the conditions. For instance, if with the same amount of wash water a longer scrubber is used, a larger proportion of products will be saved; or if in the same scrubber more wash water is used, a larger proportion of products will also be saved, but a t the same time the wash water will be more dilute and therefore the costs of refining will be greater. It is therefore necessary t o have just the proper relation between these variable factors in order t o obtain the best results. I t is hoped that these few examples of efficiency studies will indicate some of the opportunities for increasing the efficiency of hardwood distillation operations by means of technical investigations. L. F. HAWLEY. LABORATORY ARTHURD. LITTLE,INC. BOSTON
ORIGINAL PAPERS COPPER IN STEEL-THE
INFLUENCE ON CORROSION2
By D. M. BUCK
I n order t o establish the value of small amounts of copper in steel when exposed t o natural corrosion and under atmospheric conditions, a series of tests was undertaken by the writer, and in order that a thorough understanding may be had of the results of these tests, we believe i t will not be out of place to briefly describe the preparation of the steels entering into this invest igat ion. I n order to avoid the possible uncertainty in comparing different heats of steel with and without copper, and in order t h a t the conditions, except the copper content, should be identical, i t was decided for these comparisons to copperize portions of heats, leaving other portions of the same heats in their original conditions. Three heats were used: One a regular Basic Open Hearth of the following analysis: C. 0 . 1 0 ; Mn, 0.34; S, 0.034; P, 0.019. -4 second Basic Open Hearth heat was rephosphorized. giving this analysis: C , 0 . 1 3 ; M n , 0 . 4 5 ; S, 0.036; P, 0 . 0 4 2 . The third heat was regular Bessemer steel of the following analysis : C. 0.08;M n . 0.46; S, 0 . 0 7 0 ; P, 0.096. I n pouring the Open Hearth heats several ingots were first poured without the introduction of copper, then to four ingots sufficient copper was added t o obtain in two of them about 0 . 1 j per cent and the other two about 0 . 2 j per cent copper in the finished product. The Bessemer heat was treated in exactly the same way, except t h a t , since the average Bessemer heat is too small to furnish six ingots of the size de-
' Klar:
"Technologie der Holzverkohlung," p. 161. Paper presented at the Annual Meeting of the American Chemical Society, Xiln-aukee, March, 1913
447
1
sired, only two ingots were copperized, aiming a t t h e same contents as in the case of the Open Hearth. The copper was added to the molds a little a t a time a s they were filling, and that the resultant steel was uniform in its copper content was demonstrated by many analyses of the bars and of the finished sheets. Indeed, t h a t copper easily diffuses through the bath of molten steel, and does not segregate on cooling, is a well established fact. Six ingots were then taken from each of the Open Hearth heats, two normal, two with 0.1j copper and two with 0 . 2 5 copper, and three ingots from the Bessemer heat, one normal, and one with each content of copper. The fifteen ingots thus prepared were carried through the usual mill operations, each bar as cut and each sheet as rolled being chalk marked so that no confusion could possibly occur, and in the end one of each lot was again carefully analyzed as a double check on the operations. One ingot of each grade of Open Hearth was rolled into 16-gauge and the other into 27-gauge sheets, 30 inches X 96 inches, while in the case of the Bessemer steel, one-half of each ingot was rolled into 16- and the other half into a7-gauge. All grades were subjected to exactly the same treatment, being rolled by the same crews, and annealed in the same furnaces a t the same time, and the finish was such as to conform with that of the competitive sheets used in this test. From 24 t o 36 sheets of each of the 9 grades, both gauges, making 18 lots in all, were then sheared to 24 inches X 96 inches, thus obtaining a strip 6 inches wide from each sheet. These strips were sheared into 2 X 4 inch test pieces, stenciled with distinguishing marks, and were used for corrosion tests which will be described later. The 24 X 96 inch sheets were corrugated in the usual way, and
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
448
eight t o twelve sheets of each grade shipped to each of three testing stations. One of these is located in the Pennsylvania Coke Regions, where the air contains notable amounts of sulfurous and sulfuric acids and other fumes from the coke ovens. I n this district iron and steel, unless protected, corrode very fast. Another station is located on the Sea Coast, where the air carries sodium chloride. The third is in a rural community, where the air is quite pure and free from added corrosive agents. A t each of these locations a skeleton wooden building was erected, 40 feet X 8 0 feet, with a sloping roof a t a n angle of about I 8 O , with the low side about 6 feet from the ground. The buildings were entirely open and free to the passage of air on all four sides, and the roofs were uncovered until the sheets were
November, 191 I , and were entirely unprotected b y paint or other coating from the first (except the thin film of oxide always present on a n annealed sheet), allowing natural corrosion t o start immediately and to proceed without interruption. The 16-gauge sheets were placed on one-half of the roof, and the 27-gauge on the other half. The sheets a t all of the test stations were inspected from time t o time by the writer, and by other independent inspectors and within a short time after corrosion had started the higher copper steels were showing a considerable advantage over the others. Panels I , 4 and 7 (see Fig. I ) , which contain no copper, were rough t o the touch and a n examination of the surfacz of the steel under the rust gave evidence of well developed pitting. Panel I O , the low carbon
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