INDUSTRIAL AND ENGINEERING CHEMISTRY
May 15, 1933
necessitates a further separation of antimony from copper by means of sodium sulfide after the sulfide precipitate has been obtained. A few samples were treated in this manner, but no apparent increase in accuracy resulted. The presence of as little as 2 parts of antimony in 10,000,000parts of copper can be shown by this procedure. ON SAMPLES OF TABLEI. ANTIMONYDETERMINATIONS COMMERCIAL COPPERFROM VARIOUSSOURCES SAMPL~
TABLE
11. ANTIYONYI N UNMELTED COPPER SUPERIOR MINES
FROM THE
SOURCE
OB
LAKE
ANTIMONY
%
Mass copper Mass copper
Maas copper Mass copper Mass copper Mass copper
Copper oxide
ANTIMONY
%
< 0.00006 0.00002 0.00004 0.0002 0.0004 0.0004 0.001
183
Ahmeek mine Calumet and Hecla conglomerate Champion mine Isle Royale mine Osqeola mme incy mine alumet and Hecla leaching plant
?
< 0.00002 < 0.00002 < 0.00003 < 0.00002 < 0.00002 < 0.00002 < 0.00002
LITERATURB CITED (1) Bl:menthal, 2.anal. Chent., 74, 33 (1928). (2) Nitchie, IND. E m . CHEW,Anal. Ed., 1, 1 (1929).
RECEIVED December 8, 1932.
An Improved Head for Laboratory Fractionating Columns E. C. WAGNERAND J. K. SIMONS Harrison Laboratory of Chemistry, University of Pennsylvania, Philadelphia, Pa.
A
STILLHEAD for ordinary laboratory distillations on a small scale is best made wholly of glass, fitted to the column (or to several columns of different lengths or types) by means of a ground-glass seat. The head should be strong, well balanced, and free from internal complications and also from readily broken external arms If not in one piece, its parts should be connected by ground joints, rather than by rubber tubing, stoppers, etc. The head should be so designed as to provide variable reflux up to total reflux, to permit fairly accurate determination and control of the reflux ratio and accurate observation of the boiling point of the material being condensed, and also to deliver a cool distillate. Examination of a number of published designs (1-7, 9-19) shows that these qualifications are not well combined in any one head.
DESIGNOF HEAD It is believed that the design shown in Figure 1 satisfactorily incorporates the desirable features mentioned. The functions of the ground-glass seat A , the multiple ports B , and the drainage tube C are obvious. Partial condensation of vapors, yielding primary reflux, is effected by condenser D, which is cooled by water or air and is inserted through ground joint d. To obtain greater condensing surface condenser D may be made with a somewhat bulbous tip. The connecting arm E (which may be omitted) eliminates a possible dead vapor space about D. Condenser G is of double spiral type, and is seated in ground joint H . Condenser 1 reduces the temperature of the condensate. If high-boiling liquids are to be distilled, condensers G and I may be cooled by means of a current of air drawn through them, or by a stream of water passed very slowly, so that temperature differences between the hot vapor channels and the parts G, H , I , J, and K will not set up dangerous strains. The connecting tube J is of small bore (about 2 mm.), and is sloped as shown. During distillation part or all of the condensate from G and I may be returned to the column through this tube, thereby increasing the reflux, the distribution being determined by means of stopcock K . It is intended, however, that most of the reflux be produced
by condenser D, thus relieving condenser G of heavy duty during ordinary distillations, while permitting operation at high or even total reflux. With high-boiling liquids it may be necessary to use condenser D little or not a t all, as the incidental condensation in the head and the reflux through J may yield the desired reflux ratio. Tube J, because of its reduced bore, remains sealed with liquid even when all the condensate is drawn off as product. The slope of J should be slight, and the stopcock placed close to the junction, to minimize the volume of liquid held up at this point. The head is insulated, as indicated in the figure, by a covering of magnesia cement, applied as a paste made with water glass. The reflux ratio is ascertained by c o u n t i n g drops from C and from L. Drainage tube C is visible, as the column is glass-jacketed. The short enclosed-scale thermometer P is seated in a ground joint, 'the inserted half of which is i n t e g r a l with t h e thermometer jacket. The thermometer is graduated from 20' to 300" in 1'; the length of the scale is 8.5 cm. Temp e r a t u r e s are observed through a short telescope lens (the type f u r n i s h e d w i t h t h e Pregl microazotometer is satisfactory), and can be read to 0.1'. The thermometer is calibrated for immersion t o the ground joint. The arrangements shown are considered prefe r a b l e to t h e use of a thermometer-well long FIGURE 1. DIAGRAM OF STILLenough for total immersion HEAD Reduction is to one-fourth of actual of the mercury column, since Hose connections of condensers such a space, when at the size. U and I are in the rear.
184
ANALYTICAL EDITION
head of a column operated a t moderate or low rate, cannot always be assumed to be filled with the vapors a t the boiling point. ADVANTAGES This stillhead is entirely of Pyrex glass, with none but glass connections. It is compact, symmetrical, relatively small, and strong, with no easily broken projecting parts. With all condenser lines suspended the head is balanced and stable, requiring no support other than the ground-glass insertion a t A . The head can be insulated completely without obscuring the internal drip-tube C, which shows the whole of the reflux. The thermometer is mounted vertically and is properly located. Two condensers are available for increasing the reflux, which may be varied up to total reflux. The construction of this apparatus, while beyond the abilities of most amateurs, is not difficult for a good glassblower. It is of course essential that the head be properly
Vol. 5 , No. 3
annealed immediately after making. Standard taper groundglass joints (8) could probably be used a t A , d, and H. LITERATURE CITED Bruun and Sohicktanz, Bur. Standards J. Research, 7, 851 (1931); Bur. Standards, Research P a p e r 379. Clarke and Rahrs, IND. ENG.CHEM.,15, 349 (1923); 18, 1092 (1926).
Fenske, Quiggle, and Tongberg, Ibid., 24, 409 (1932). Hill and Ferris. Ibid.. 19. 379 (1927). H o h e n , “Meihoden’ de; organisohen Chemie,” 3rd. ed., Vol. I, 11. 591, G. Thieme, Leipzig, 1925. ENG.CHEM.,Anal. Ed., 3 , 3 7 3 (1931). Kee:er and Andrews, IND. Les’ e and Geniesse, IND.ENG.C H ~ M1. 8, , 5 9 0 (1926). Lev*tt. Ibid.. News Ed.. 10. 268 (1932). Lovele‘ss, IN;. ENG.CH‘EM.; 18, 826 (1926). Marshall, Ibid., 20, 1379 (1928). Marshall and Sutherland, Ibid.. 19, 735 (1927). Peters and Baker, Ibid., 18, 69 (1926). Rmcnrvsn February 11, 1933.
A Method of Determining Solvent Properties of Volatile Thinners in Varnishes MIKKELFRANDSEN,~ The Cook Paint and Varnish Company, Kansas City, Mo.
V
ARIOUS tests have been designed to determine the for one hour in a water bath maintained a t 25” C. They solvent properties of volatile thinners used in the were then examined for a precipitate, which, forming a lump manufacture of varnishes: titration with the thinner a t the bottom of the tube, or adhering to the glass, was easily of a heavy-bodied linseed oil, a solution of kauri gum in recognized by slowly turning the tube upside down. To inbutyl alcohol, or a solution of a distillation residue of kauri crease the accuracy, a new series of determinations was made gum in turpentine, or gradual addition of the thinner to a between the last tube without a precipitate and the first tube short oil-kauri varnish of standardized composition as de- with a precipitate-for example, between the tubes conscribed by Holley ( I ) , until precipitation occurs. These taining 0.6 and 1.0 volumes of thinner, respectively. With tests, however, can hardly be expected to give accurate in- most thinners, the minimum volume causing precipitation, formation about the relative solvent powers of various designated as solvent power, could easily be determined with thinners in varnish bases that may contain no kauri gum at an accuracy of 10 per cent. all but instead various combinations of other resins of quite different solubilities (2). Moreover, it is to be expected that TABLEI. SOLVENT POWER OF PETROLEUM DISTILLATES other ingredients of the varnish base, such as tung oil and SAMPLD DISTILLATION RANQD SCLVDNT POWER c. linseed oil, will affect the solvent power of the thinner in the 1 37-217 0.7 mixture, because the solvent power of a mixture usually 2 38-222 0.6 3 94-174 0.8 differs widely from that calculated from its composition and 4 99-175 0.7 the solvent powers of its components. 149-188 5 1.0 144-206 0 .7 6 It seems preferable, therefore, in each case to measure the 146-222 7 0.8 147-229 0.8 8 solvent power of prospective thinners by the amount of 150-228 9 0.8 thinner that will cause incipient precipitation from the par183-249 10 0.9 184-254 11 1.6 ticular varnish base with which it is to be used. By this 0.5 12 method the writer was able to select the proper thinner for 0.6 13 a varnish in which precipitation formerly would take place 0.4 14 15 0 .6 on standing. Several difficulties, however, made an ordi0.6 16 0 . 6 17 nary titration useless. The precipitation of gum, caused 18 0.7 by adding too much thinner to the varnish base, took place 0.7 19 20 0.7 very slowly, and the varnish was so dark in color that the 21 0.7 22 0.9 precipitate could not be readily discerned; furthermore, the temperature of the solution had some effect upon the 23 99-107 0.6 107-121 24 0.7 point of precipitation. As a result, the procedure was modi121-135 0.7 25 135-149 0 .7 26 fied as follows: 149-163 0.8 27 Into each of five graduated test tubes were poured 5 to 0.8 Residue 28 10 ml. of varnish base, and the volume in each case was read off to 0.1 ml. To the five samples were then added 0.3, 0.6, Some results of this test applied to various petroleum dis1.0, 1.5, and 2.0 volumes, respectively, of the thinner to be tillates are given in Table I. Samples 1 to 11 are refined tested, and the samples were shaken thoroughly and left commercial petroleum fractions. Samples 12 to 22 were obtained by Engler distillation of sample 2, and samples 23 1 Present address, U. 6 . Bureau of Standards, Washington, D. C.
