INDUSTRIAL A N D ENGINEERING CHEMISTRY
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as well as all handling of the tubes, is above the point where the light strikes the tubes much better comparisons can be made. Keep the glass tubes clean by using a rod with a soft piece of cloth fastened a t one end. Soap should be used frequently in cleaning, but the tubes should always be rinsed thoroughlyafter using it. Do not insert the cloth into the tubes while dry, for fine grit may be present and scratch the glass. Use care in removing and inserting the tubes so as not to scratch the outside. The tubes must be kept in perfect condition if accurate results are to he obtained. Turn on the light only when an observation is being made, and then
Vol. 18, No. 3
turn off immediately. Otherwise the paint on the inside of the turbidimeter may be affected by the high heat from the lamp. The turbidimeter is designed for testing only turbidities less than 2, and is not accurate above this amount. If i t is desired to test water with a higher turbidity dilute with zero-turbidity water until the amount is below 2. Color below 10 does not appreciably affect the results, but if higher than this amount make a color determination on the sample and adjust the color of the standard to approximately this amount.
Effect of Splitting on the Tensile Strength of Leather' By John Arthur Wilson and Erwin J. Kern A. F. GALLUN&
SONS
HE tensile strength of leather is not uniform throughout
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its thickness. The outer layer, which constitutes the thermostat layer of the living skin, is relatively very weak, nearly all the strength of the leather being in the reticular layer. Any reduction of thickness of leather thus tends to alter its tensile strength and may either increase or decrease i t per unit cross section depending upon the strength of the part removed. It is thus apparent that the extent to which leather has been split or shaved in process of manufacture will affect the results of any experiments in which the tensile strength is the dependent variable. As a guide in such experimental work, two charts have been prepared showing how the strength of vegetable- and chrome-tanned calf leathers varies as the grain or flesh layer is reduced in thickness. A number of representative skins of finished vegetable- and chrome-tanned calf leathers were selected. On either side of the backbone of each skin, and with length parallel to it, a n area 15.24 X 63.50 cm. was cut so that the inner edge was about 10 cm. from the backbone and the ends equal dis1
Received October 17, 1925.
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Co., MILWAUKEE, WIS.
tances from the head and tail ends of the skin. This end was then cross cut into twenty-five strips each 15.24 x 2.54 cm., numbered consecutively. The odd numbered strips were tested for tensile strength exactly as described in an earlier paper.2 All leatber when tested was in equilibrium with a n atmosphere of 50 per cent relative humidity. The results were used to calculate the strengths of the even numbered strips, which were assumed to be the average of the strengths of the adjoining strips. For example, the average strength of strips 3 and 5 was assumed to be the strength of 4. I n general this will be true, so that reliable results may be assured if the test is repeated several times. Each even numbered strip was split on a band knife machine into two layers. I n 2 the splitting was done so that the grain layer was 10 and the flesh layer 90 per cent of the total thickness; in 4 the grain was 20 and the flesh 80 per cent of the total thickness; and so on. The strength of each split was then measured and compared with the calculated strength of the unsplit strip. f
Wilson, THISJOURNAL, 17, 829 (1925).
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Gmln S p l i t s 100
90
80
70
60
SO
40
30
20
10
100
0
90
80
70
Flesh S p l i t s
Per Cent of Total Thiahess Figure 1-Relative Strength of S Hts of Vegetable-Tanned Calf Leather ComDared wfth UnsDlit Leather The rtren h is calculated per unit width, not cross section. Average t e n s e strength = 324 kg. per sq. cm. Average thickness 0.91 mm.
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Grain S p l i t s 60 50 40 Flesh S p l i t s
30
20
10
0
Per Cent o f T o t a l Thickness Figure %Relative Strength of S lit8 of Chrome-Tanned Calf Leather Compared wit[ Unsplit Leather The strength is calculated per unit width, not crass rect!on. Average tensile strength 268 kg. per sq. cm. Average thtckness 1.04 mm.
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March, 1926
I S D USTRIAL, A X D ENGINEERING CHEJIISTRY
For each kind of leather the entire experiment was repeated several times to insure reliable results, and these are plotted in Figures 1 and 2. Elach figure has a pair of cross lines and three curves, one of which represents the sum of the other two. The curves represent strength per unit width, not cross section. However, the strength per unit cross section can be obtained from the figures and its variation is indicated by the relation of the curves to the cross lines. Where the curve is above its corresponding cross line the strength per unit cross section has been increased by splitting and where below, it has been decreased. Cutting away the grain layer to a depth less than 48 per cent for the vegetable-tanned leather or less than 22 per cent for the chrome increases the strength per unit cross section of the remaining flesh layer, because the grain portion of the leather is so much weaker than the flesh portion. Splitting always causes a loss in strength per unit width and the sum of the strengths of the two splits is always less than the strength of the unsplit strip. This is shown by the uppermost curve in each figure. The distance of’ this curve from the 100 line gives the total loss in strength of the leather due to splitting. If the chrome leather is split into two layers of equal thickness, the grain layer will be only 26 and the flesh layer 16 per cent as strong as the unsplit leather, making a total loss of strength of the original leather of 58 per cent. This excessive loss in strength of the flesh layer is the result of the severing of the fibers in splitting, which is likewise responsible for the great loss in strength of the leather as a whole. It does not indicate weakness of the reticular layer
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compared with the thermostat layer. On the contrary, cutting away the thermostat layer (one-sixth of the total thickness) increases the strength of the flesh layer per unit cross section, while the grain layer suffers a loss with the removal of any amount of flesh layer. The greater looseness of structure of the chrome leather is responsible for the greater maximum total loss of strength, 60 per cent for the chrome against only 48 per cent for the vegetable-tanned leather. This is also shown in the greater weakness of the chrome flesh layers. I n the chrome leather the flesh is weaker than the grain when i t is less than 53 per cent of the total thickness; in the vegetable-tanned leather the flesh is the weaker only when it is less than 41 per cent of the total thickness. The writers’ experiments upon heavy leathers indicate that the effect of splitting is similar in kind but not in quantity to that here described. It must be remembered that the ratio of thickness of thermostat layer to reticular layer decreases with increasing thickness of the original skin. The resistance of the leather to stretch was found to vary directly with the strength. Measurements were made of the load in kilograms required to stretch each strip to 1.25 times its initial length and this value was called R , or the resistance to stretch. Splitting caused a percentage decrease in the value of R for both grain and flesh splits identical with the percentage decrease in strength. Thus Figures 1 and 2 may be used to indicate the resistance of the leather to stretch simply by calling the ordinates “per cent of resistance to stretch of the unsplit leather.”
Elimination and Recovery of Phenols from Crude Ammonia Liquors’ By Robert M. Crawford THE MCALEENAN CORP.,PITTSBURGH, PA.
ASTE liquors from coke-plant ammonia stills constitute a known source of stream pollution due to the presence of very appreciable quantities of phenol and cresols, which are scrubbed out of the gas by the flushing liquors and which ultimately reach a stream via ammonia still wastes. I n the crude ammonia liquor the phenols exist in solution in the “free” state, but when lime is added in the still to decompose the fixed ammonia, most, if not all, of the phenols are “fixed” and pass into the still waste as calcium phenolates. This “fixing” of the phenols probably explains why the phenols are not often found in the free state in the still wastes. However, owing to the absorption of carbon dioxide from the atmosphere adjacent the waters of a stream, or perhaps to mineral acids in the stream, the phenolates are decomposed, liberating the phenols in free state. The free phenols thus constitute a source of stream pollution. This liberation may take place a t a considerable distance down stream from the offending coke plant. I n order to prevent such stream pollution, i t has become customary practice in the coke-oven industry to quench the hot coke with ammonia still wastes, which affords a 6 h p k and easy means of disposal. This method, however, neems t o have certain obvious objections. (1) The phenols are completely vaporized with the water and are dissipated into the atmosphere only to condense and collect on sur-
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Received January 15, 1926.
rounding territory, perhaps to be washed into a stream by natural rainfall; (2) corrosive compounds contained in the still waste, or formed during quenching of hot coke, give rise to rapid deterioration of quenching equipment; (3) a marked discoloration and a disagreeable odor are imparted to the coke, which affect its sale for domestic purposes; (4)if suspended calcium salts exist in the still wastes, clogging of the coke pores results, which prevents the free burning of furnace coke. I n investigating commercial means for the possible recovery of the phenols from the crude liquor, the writer recalled a method used early in the World War for recovering phenol from the waste liquors from synthetic phenol fusions. This method consisted simply in extracting the waste liquors with benzol, which dissolved out the phenol. Dawaon’ describes a similar method used in England for the same purpose. For the recovery of the phenol from the benzol extract, the method suggested by Weiss in 1916 offered the most likely procedure which was to remove the phenol from the benzol extract by means of a solution of caustic soda. These basic methods of procedure offer practical possibilities which have been demonstrated successfully on a commercial scale by the Foundation Oven Corporation’s installation for the Hudson Valley Coke & Products Corp., at Troy, N. Y. ; and similar installations by the National Tube Company * J. SOC.Chcm. I n d . , S9, l S l T (1920).
