November 15, 1941
ANALYTICAL EDITION
This method is rapid and lends itself to mass production methods. It has considerable applicability and gives as good a precision as older methods based on the use of an acetylating agent. I n the case of the phenols the results in general were superior. From the results in Table I i t is apparent that several limitations are imposed by the character of the molecule undergoing esterification. The effect of solubility in this connection has been noted by others (6). I n initial experiments with mannitol low results were obtained. Whenasmall amount of water was added to this compound the acetylation was almost complete. The interference of several functional groups-for example, aldehyde and nitroso-with indicators was observed. This made titration by the usual methods impossible. Side reactions involving the liberated hydrogen chloride may account for several unusual results, particularly in the case of such olefinic compounds as geraniol, linalool, and isoeugenol, and may explain the unusual behavior of alpha- and beta-naphthols in which one ring readily forms addition products (7). The data obtained with tertiary alcohols can also be explained on this basis, since such alcohols are known to react readily with hydrogen chloride (7). Interesting observations were noted in the studies of the substituted phenols. As indicated in Table I, the more
823
acidic phenols such as picric acid were not acetylated. This was to be expected, as the hydroxyl group is more acidic than phenolic in character and therefore behaves as an acid (7). The failure to acetylate salicylic acid and its isomers cannot be adequately explained on this basis; perhaps it is more a question of chelation. It is evident that such factors as solubility, chelation, unsaturation, enolization, and rearrangement are important in determining the hydroxyl content of organic compounds by the use of acetyl chloride.
Literature Cited (1) Linderstrom-Lang, K.,and Holter, H., Compt. rend. trap. Eab. Carlsberg, 19, No. 4 (1931); 2.physiol. Chem., 201,9 (1931). (2) Marks, S.. and Morrell, R. S., Analyst, 56,428 (1931). (3) Normann, W.,and Schildknecht, E., FeUchem. Umchau, 40, 194 (1933). (4) Peterson, V. L., and West, E. S., J. Biol. Chem., 74,397 (1927). (6) Smith, D.M., and Bryant, W. M. D., J . Am. Chem. Soc., 57,61 (1935). (6) Verley, A,, and Bolsing, F., Ber., 34,3354 (1901). (7) Wertheim. E.,“Textbook of Organio Chemistry”, Philadelphia, P. Blakiston’s Son & Co., 1939. (8) Williams, R. J., “Introduction to Organic Chemistry”. p. 576, New York, D.Van Nostrand Co., 1935. PUBLIEHED with the approval of the Monograph8 Publioatiom Committee, Oregon State College, as Research Paper No 49, School of Science, Department of Chemistry.
A Method of Installing Tube-Wall Thermocouples E. L. PATTON AND R. A . FEAGAN, JR., United States Department of Agriculture, Naval Stores Station, Olustee, Fla.
Rietschel (6) installed the thermocouple junctions in grooves in the wall of a pipe or tube and brought the leads out in grooves covered over with litharge and glycerol cement. Reiher (6) and Colburn and Hougen (3) also used a groove installation and depended on litharge and glycerol cement for insulation, although the leads were finally brought out through the hot vapors. McAdams (4) gives an excellent discussion of the measurement of surface temperature, citing the literature on the subject. ColBaker and Mueller ( 2 ) used an installation similar t o that of burn and Hougen (3) also discuss the errors resulting when therColburn and Hougen, in that a groove was cut three quarters of the distance around the tube and the junction was installed in a mocouple junctions are installed directly on the surface or when drilled hole at the end of the groove. The leads were sealed into the leads are brought out through a medium either hotter or the groove and finally c:trried out through the hot vapors. Varicolder than the junction. All workers agree that it is advisable ous methods of sealing the lead wires into the groove were tried to bring the leads from the thermocouple junctions through a Substantially isothermal zone (as through the metal wall itself by Baker and Mueller who state that “pure Bakelite varnish plus rather than through the fluid stream), but McAdams states that a filler had a tendency to shrink and crack in service. Litharge the difficulty of construction has probably prevented wide use of and glycerol cement disintegrated. Lithar e and glyperol cement this method. with a covering of the Bakelite varnish a%o failed. ’ This was probably due to the fact that they condensed vapors of organic compounds as I I well as steam. In the method finally . ANY DESIRED DISTANCE adopted, they enclosed the leads in small JVNCTION brass tubes and sealed them intothegrooves BRASS TUBE A-1 with solder which was polished until flush -~-..-~--------------~ - - - - - - _ - - _ _-_-_._.---,__ _ _ _ _ with the surface of the heat transfer tube. However, the leads were brought out of the condenser shell through the hot vapors. Akin and McAdams ( 1 ) installed thermocou le junctions in holes drilled tangential& in the wall of the heat transfer tube and insulated the lead wires with Pyrex capillary tubing.
T
HE determination of heat transfer coefficients through liquid films requires a method of measuring tube-wall temperatures.
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FIGURE1. DETAILS OF INSTALLATION
I n investigating the heat transfer coefficientsfor the condensation of mixed vapors of turpentine and water on a single horizontal tube, the authors sought a method of tube-wall thermocouple installation which would meet the following stipulations: (1)lead wires to be brought out entirely through a substantially isothermal zone; (2) no insulation to be exposed to turpentine, which readily attacks and softens litharge-glycerol cement and similar materials; (3) con-
INDUSTRIAL AND ENGINEERING CHEMISTRY
824
struction to be sufficiently simple to be performed in the average machine shop at moderate cost. The method which was finally rvorked out apparently satisfies these conditions. Details of the installation appear in Figure 1, which shows only the tube and the method of installing the thermocouple junctions in the tube wall. This tube could be that of a single-tube test
l-ineh, ekraheavy copper pipe. A slot is milled in the outside v d l of the tube, parallel to the longitudinal axis, from the point at which the junction is t o be installed to a point where the leads may be brought out,without influencing the transfer of heat or the flaw of flmds. Thls operation is easily performed in a well-equipped machine shop. The junction is installed in a 0.062-inch hole drilled 0.25-inch into the tube wall at an angle from the slot. The junction is inserted in this hole and soldered in place. The leads am enclosed in a small brass tube and laid in the slat. The brass tube is bent slightly at the end and butted against the wall of the slot, in such a. way that it completely covers the leads. The slot is then filled in with solder and is polished down t o the original contour of the tube. The size of the slot depends on the size of the brass tubing necessary t o enclose the leads. For a pair of No. 24 enameled, silkcovered wires, a brass tube 0.093 inch in outside diameter and 0.071 inch in inside diameter will be found satisfactory. This tube will fit nicely in a milled slot about 0.10 inch wide and 0.10 inch deep. By making the slot wider, two or three sets of leads may be brought out from each end of the tube, and if more
Vol. 13, No. 11
than four to six couple installations are desired in one tube wall, the number of slots may be increased. This method of installation may be used to locate a thermocouple junction a t any point in the wall of the tube and the leads may be carried to any desired point through a substantially isothermal zone. The possibility exists that the solder, having surface characteristics different from those of the tube metal, might influence the flow of condensate over the surface of the tube. This effect could be eliminated by plating the surface of the tube after the thermocouple installation. If the heat flux is high, a correction should be made for the temperature drop between the tube surface and the point of junction installation. This can easily be done when the heat flux and the thermal conductivity of the tube metal are known.
Literature Cited I(1) l l Akin, Akin. G. A,. McAdams. W. H., H..Trans. Am. Inst. Chem. A,, snd and McAdams. C h m . Enm.. Engr.. " . . ~ I ~~~
35, i37-55 35, 137-55 (1939). (2) Baker. E. M., and Mueller. (2) Mueller. A. C.. IND. ENG.CHEM.,29, 106& 72 (1937); Trans. Anz.Inst. AmInst. Chem. Engr.. 33,539-58(1937). (3) Colburn and Hougen, IND.ENO.CHEM.,22.522 (1930). 14) MoAdzms. "Heat Transmission". New York. MoGraw-Hill Book Co., 1933. (5) Reiher, H., Mitt. Forschungsarbdtungm, No.269 (1925). (6) Rietschel, Mttt. Pw2fungsanstolt Hdaungs LOftungsdnrichtu?wm, RBnigl. Tech. Hochsehule Berlin. 3 (1910).
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G . FRED1 LICK SMITH, Wm. Albert Noye
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alkaline solutions presents a special problem in apparatus assembly. Where the liquids involved are not particularly corrosive Johnson and Miller (1) suggest the use of centrifuge cups and receivers machined from Lucite. The present description involves au improvement, since standard parts are involved and possible interaction of equipment and reagents is eliminated. The apparatus is shown in Figure 1, mounted on an Interns* tionrtl centrifuge siae 2 (International Equipment Company, 352
am mtn ruooer cusnron inserc no. OXL ana Dome no. am, cub into two parts and the top discarded. The special centrifuge onps were made by the Coon Porcelain Co. The centrifuge cups are 8.57 om. (3.375 inches) tall with an outside diameter at the base of 4.13 om. (1.625 inches) and at the top of 6.72 cm. (225 rnrhes). The imide dimnletcr at the to ill 64 CUI. (2.125 inches) and the upper flange is 1.75 rm. ( I l l 6 inch) a,idr and id offtict 0.32 cm. (0.125 inehl t o orowdc a shoulder SUEnortontopofthetrunnion&p. Thei6nsidideptbis8.26cm. (3.25 Cnches) a i d the capacity is f70 mL The cups are glazed inside and outside except for the bottoms. There are 190 t o 200 er forations in the bottom, all less than 0.05 em. (0.02 inchy i, diameter. A second o5set 3.33 em. (Is/rs inches) from the t O D is 0.16 em. (I/>e inch) in depth. The lids, are standard dize Coors No. 4 crucible lid. The cup and hd weigh 177 grams (6.25 ounces). The Hter flask assembly in the background is for use in removing excess mother liquor by reduced pressure filtration. The filkrflnskis:oful0Bml:capn&y provided aitlia l O . l t ~ - ~ (4-inch) u. (i0" funnel. The ~ u p p ~for m LIE ccntriiugc cup is nude aecordmr I O rhr directions oi Smith and Gina I?) from a So. 14 rubber turyed inside out. The assembly as described will provide for 0.45 kg. (1 pound) of crystals of average density and the equipment can be whirled at 2000 r. D. m. sumorted in trunnion No. 236 without daneer of prriwutini the fl
