V O L U M E 2 2 , NO. 4, A P R I L 1 9 5 0 generally three times. Wash the cotton filter with chlorolorin, and make up to volume with chloroform. Transfer the solution to a photoelectric colorimeter and read, having previously sei the instrument to zero with chloroform. Analysis of Textile Material. Take a piece of material that i h expected to have no more than 0.5 mg. of surface-active material present and place in I) 125-ml. separatory funnel. Extract with 100 ml. of hot isopropyl alcohol which has been heated on a steam bath. Extract with 20 ml. of boiling water to free absorbed alcohol, and compress material with a stirring rod as much as possible. Place the extract in a dye beaker in a steam bath and drive off all alcohol, as determined by odor and cessation of bubbling, but do not allow the evtract to go to dryness. The residuc should be 20 ml. or less. Transfer to a separatory funnel and proceed ELS n-ith solutions. SUMRI 4RY
At an acid p1-I basic fuchsin nil1 react quantitatively with dodecylbenzene sodium sulfate, giving a chloroform-soluble magenta-colored extract which may be measured in a photoelectric colorimclter. The method is accurate and simple. The method is norispccific, as side reactions nith groups other than the sulfite group can occur; however, there is no interference from sodium sulfate, which does not precipitatc basic fuchsin or form a chloroform-soluble complev I\ ith ba5ic fuchsin. Sodium sulfate does not react with methylene blue. Thcx fact that b u i c fuchsin is not a specific reagent for suifacc-
617 :ic*tivt. :igcwt,s is not believed to hinder its use.
Although this nicthotl \vas actually calibrated for only one compound, the :ruthor has made numerous calibrations wit'h the methylene blur method, and found that side reactions did not interfere other than to produce a deviation from I3ecr's lam, making it necessary t o plot a curve. lIaximum accuracy cannot be achieved with readings that are caither very high or very low. With instruments giving a reading i n per cent transmittancy, the minimum error will occur at 36.8y0 transmittancy ( 6 ) . Ayres shows that greatest accuracy is obtainable over the transmittancy range of 20 t o 60% for photometric analysis (1). A small experimental error is magnified more on a percentage basis in the lower concentration rapgcs t,h:iri in the higher ones. LITERATURE CITED
( I ) Ayres, G. H., ANAL.CHEM.,21, 652-7 (1949). (2) Gutzeit, G., Hela. C h i m Acta, 12, 713 (1929). (3) Jones, J. H., J . Assoc. Ofic. &r. Chemists, 28, 399-409 (l!l45). ( 4 ) >fellan, Ibert, "Organic Reagents in Inorganic Analysis." Philadelphia, Blakiston Co., 1941. ( 5 ) Schiff, H., Ann., 140, 93 (1866). (6) Tmyman, F., and Lothian, G . I?., I'roc. P h y s . SOC.(Lomfori),45, 643 (1933). Its(.t~vr:uFebruary 24, 1949
Kelly Tube for Sedimentation Analysis S. C. SANE, 11. K. SHIRPURKIR, V. 1.. DESIEPANDE,
AND
hl. S. 'I'EL4NG
Laxntinurayan Institute of Technology, "Vagpur University, .Vagp[ir, Indin
AY'EKS (1-3, j,6,9,10) dealingwith improvements in thetechIr)nique of sedimentation analysis with the Kelly tube include elaborate calculations of the correction factor to be included i i i the original Kelly equation ( 4 ) to account for the progressive increase in the liquid level in the settling tube due to the recession of the liquid from the capillary side arm. The present paper describes a. practical device for maintaining the liquid level in the settling tube constant so as to retain the validity of the original equation. The uncertain errors caused by ordinary methods of measuring the angle of inclination of the capillary side arm of the Kelly tube in the working position of the apparatus
W Figure 1.
Constant-Level Device
after it is placed in a theinlosttitic bath have been one of the niiijor drawbacks of Kelly's apparatus ( 7 , 8 ) . Because the sign of tlic angle of inclination is directly utilized in calculating the distribution of the particle size, the need for a precision determination of the angle cannot be overemphasized. The constant-level device is further useful in the precision determination of the angle of inclination of the capil1ar.v side arm. CONSTANT-LEVEL DEVICE
In Figure 1, test tube B with a side hole, H , a t M is firmly clamped a t a predetermined height to receive the overflow and hence to function as a self-operating constant-level arrangement. The amount of overflow and the consequent loss of solid particles from the suspension (which is usually dilute) are very insignificant; a recession of 10 cm. in the capillary (usin Kelly's dimensions for the apparatus) is equivalent to 0.3 ml., wkich may correspond to the total recession a t the end of an experiment. A t the commencement of the experiment, a little excess of the suspension is poured into the settling tube, t o ensure that AI has been reached. Because the suspension is turbid, it is not possible to observe whether or not the excess has entered B , but this can be ascertained by inserting a narrow glass tube and emptying B by applying suction. The volume displaced by the immersed portion of B must be taken into consideration, while calculating the volume of the suspension under investigation. The self-adjusting constant-level device eliminates the pcrsonal error of the observer in noting the initial level, particularly with turbid suspensions, The extreme importance of niaintaining the level constant is appreciated if it is realized that a difference of 0.1 mm. in the level at M will cause a difference of O.l/sin b = 3.82 mm. in the horizontal portion of the capillary, i f Lb is 1.5". Alternative arrangement can bc made to maintain the liquid level constant-e.g., a side tube, C (shown in Figure l), may be joined a t M to permit the overflow. Such devices demand very accurate glass blowing for joining the tube in a required position The device suggested in Figure 1 using test tube R can be easily constructed and readily assemhletl.
ANALYTICAL CHEMISTRY
618 PRECISION DETERMINATIOh OF 4 N G L E OF INCLIN4TION OF CAPILLARY S I D E ARM
If the settling tube, A , is filled with water up to any convenient levels, MI and M 2 , corresponding positions of water in the capillary side arm will be L1 and Lp, respectively. Designating the vertical difference between M I and Mp as Ah and the linear recession from L1 to LZas L , we have sin b = A h / L . Although L can be measured with reasonable accuracy on a linear scale, Ah cannot be directly measured with precision orsing to parallax errors when reading the meniscus in A . The degree of accuracy desired in measuring Ah will be evident from the following calculations. Using Kelly's dimensions for the apparatus, for a maximum possible value of L = 20 em. with L b = 1.5', sin b = 0.0262 giving Ah = 0.524 cm. To obtain sin b with an error not exceeding *l%, it is necessary to read Ah = 0.524 A 0.006 em. In view of this difficulty, the device described below is used to estjmate indirectly the value of Ah to the desired degree of precision. In Figure 1, a pin is attached along the inner side of B a t its mouth with molten wax so that its point, PI, protruding above the mouth of B well above the thermostatic bath level, serves as a point of observation through a vernier microscope traveling vertically. G is a close-fitting tube of glass or metal such as a cork borer, firmly clamped, serving as a guide sleeve. The true vertical movement of the microscope can be tested by observing the path of movement of the microscope cross wire along a plumb line suspended in front of the microscope objective. By bringing P1always a t the intersection of the cross wires in the microscope eyepiece, the vertical movement of B in the plane of the optical avis of the microscope can be ensured. AT1and N z are two plumb lines forming a vertical plane nearly a t right angles tq the optical ayis of the microscope. If PI is also brought in plane with iV1 and AVpwhich can be inspected visually, a really vertical movement of B through G can be guaranteed. B is slowly lowered into A filled with water and clamped so that some water enters B through the side hole in position H I , the meniscus in A being a t Ml. The readings for P1 on the microscope scale and for L1 on the linear scale are noted. 4 small quantity of xater from A is removed by means of a pipet, so that level Lz is nearly approached. Then B is further lowered until more water from A enters B through the side hole in position
H2 and B is again clamped. Thus, M1is altered to M Zand L, recedes to L2. The readings of Pz and LZare again noted. The difference between M iand M 2 is obviously equal to that between HI and Hp and therefore equal to that between P1 and Pz. Hence, Ah corresponds to the vertical movement of the pin point from P1 to Pp which is accurately recorded by the microscope. In this method, levels M 1 and Mz are automatically adjusted by the positions of H1 and Hp, provided water is caused to flow into B a t the time of adjustment; this step is absolutely essential. Parallax errors are eliminated, as the direct observation of the liquid meniscus is avoided.
The precision of this method depends upon the least count of the vernier scale of the microscope. This method has given constant and reproducible results for a given setting of the apparatus in its working position. A cathetometer can be substituted for the microscope. This method is independent of the bore dimensions of tube A and the capillary side arm. LITERATURE CITED
(1) Dotts, \y.hf., IND. ESG.CHEM.,A N ~ LED., . 18, 326 (1946).
(2) Duncombe, C. C., and Withrow, J. R., J . Phw. Chem., 36, 31 (1932). (3) Jones, F. R., and Barlow, C. G., J . Soc. Chem. Ind., 62, 129 (1943). (4) Kelly, W. J., Ind. Eng. Chem., 16, 928 (1924). ( 5 ) Kramer, E. O., and Stamm, A. J., J . Am. Chem. SOC.,46, 2709 (1924). (6) Lambert, R. H., and Dotts, W. AI., IND. ENQ.CHEM.,ANAL. ED.,19, 283 (1947). (7) Lambert, R. H., and Wingham, E. P., J . Optical SOC.Am., 11, 393 (1925). (8) Stamm, A. J., Colloid Symposium Monograph, 2, 70 (1924). (9) Sumner, C. G., J . Faraday Soc., 28, 20 (1932). (10) Sumner, C. G., and Lambert, R. H., IND. ENQ.CHEM.,ANAL. ED.,19, 939 (1947). RECEIVED May 10, 1948.
Adjustable Constant Flow Regulators for Corrosive Gases EARL J. SERFASS, DAVID A. SHERMER, A N D RALPH G. STEINHARDT, JR. Lehigh University, Bethlehem, Pa.
HE apparatus described were designed specifically for obTtaining a continuously adjustable constant flow rate of chlorine, but, by suitable modification of the experimental arrangement, regulator liquid, and trap solution, it may be used either as a constant flow regulator or as a manostat for any gas. Furthermore, two regulators may be used to obtain a constant flow of gas through a system at constant pressure. In the simple regulator shown' in Figure 1 the lower chamber is about four fifths filled with concentrated sulfuric acid. Tube A is connected directly to the chlorine supply. Tube B is attached to a capillary flowmeter, F , which in turn is connected to the system. Tube C is connected through a trap containing concentrated sodium carbonate solution to a water-jet air pump. Tube D is open to the atmosphere. A rubber aspirator bulb is attached to tube,E. The regulator is placed in operation by first forcing about half of the acid into the upper chamber. After the air pump is turned on, the chlorine supply is adjusted to give a bubble rate of from 1 to 10 per second. The flow rate is adjusted by raising or lowering the liquid level in the upper chamber. If the bubble rate is excessive, chlorine will be forced out of tube D,the flow rate will vary erratically, and the greater part of the chlorine will be wasted. The regulator will not give a rigorously constant flow rate until the acid has become saturated with chlorine. Small cyclic rate variations corresponding to bubble formation may be largely eliminated by placing a %liter reservoir between the regulator and the flowmeter. The dimensions of the regulator are not critical, with the following exceptions: The diameter of tube D must be large 0 so that the pressure drop through it is very enough ( ~ 1 mm.) small; otherwise the flow rate will vary as a function of the pumping velocity. The annular distance in the upper chamber
should be at least 1 cm., in order that the liquid head vary as little as possible. The diameter of the bubble outlet should be about 10 mm. In the regulators in use in this laboratory, the
Figure 1.
Flow Regulator
