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metric method. Some scattered light was no doubt present in the radiation employed in the above visual measurements, Instrument design and quality of optical parts are important factors. With the photoelectric filter photometer, absorption values obtained were much too low, indicating that other lines were not sufficiently removed by the filter combinations. It was concluded that the group of lines near 4358 A. was not completely isolated by the filters available and that such filters alone are inadequate to isolate the 4916 A. line. These filters are thus inadequate to permit an analysis of this carotenoid mixture with a photoelectric filter photometer. These analytical constants and this limited experience with the visual method are presented in the hope that they may be useful to workers employing visual equipment. It is noted that Equation 4 (1) fcr calculation of per cent /3-carotene is simplified for A4916 A. because the denominator becomes 100, the difference between the specific absorption coefficients. It is highly probable that the new types of photoelectric spectrophotometers, which have recently appeared on the
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market at comparatively low cost and which employ a mercury arc source, would isolate these mercury lines sufficiently well and also provide greater precision and speed than are possible with the visual method.
Summary &carotene and neo-p-carotene can be determined in properly purified solutions from spinach extracts by means of a visual spectrophotometer, preferably with a Type A-H4 mercury lamp. A photoelectric filter photometer did not isolate sufficiently narrow spectral regions for accurate analysis of this carotenoid mixture. Tke total carotene is calculated from the absorption at 4358 A. and the percentage of either carotene from the absorptions a t 4358 and 4916 A.
Literature Cited (1) Beadle, B. W., and Zscheile, F. P., J. Bid. Chem. 144, 21 (1942). JOURNAL
Pager 6, Purdue University Agricultural Experiment Station.
This research was supported in part by a General Foods Corporation Fellowship.
Pipet-Type Capillary Viscometer For Substances Which Are Solid or Highly Viscous at Room Temperature J. F. WEILER, Coal Research Laboratory, Carnegie Institute of Technology, Pittsburgh, Penna.
T
HIS viscometer was developed for routine determina-
tions of the kinematic viscosities of the heavier products resulting from the destructive hydrogenation of coal, These products have a low viscosity index and, although sufficiently fluid at 98.89' C. (210' F.) to permit the use of a capillary viscometer, are either solid or highly viscous at and considerably above room temperature, so that the charging of an Ostwald viscometer is difficult. The several modifications of the U-tube viscometer having automatic or nonautomatic accurate charging features have r e c e n t l y b e e n briefly discussed (3). However, for ease of charging and cleaning, size of sample required, and recovery of the sample, none is as convenient as the pipet-type viscometer such as described by the Bureau of Standards ( 2 ) . A serious disadvantage of this instrument is that it requires a special constant-temperature bath from which it cannot be removed without disturbing the bath, The so-called Bureau of Mines pipet viscometer (1) can be handled in the same manner as the Ostwald type, in that several viscometers may be installed in the same bath and can be removed and replaced without disturbing the bath. The pipet, however, must be charged while out of W CAP the bath. This limitation not only causes difficulty in charging materials which do not flow readily a t room temperature, but also necessitates removal
of the pipet for recharging for a check determination. The viscometer described in this communication makes use of a novel method of handling the sample to secure the advantages of both of the above cited modifications of the pipet viscometer. METHODOF USE. The sample (5 to 10 cc.) is contained in a sample vial of 15-cc. capacity having a screw cap. With the viscometer removed from the bath, vessel 4 is detached at the ground joint and the sample vial is screwed into the sample mal cap which is suspended b a thread leading up through support arm B of the viscometer. T i e crown of this cap has been cut out,.sa that the pipet tip can pass through it. A is fastened in place with springs and the viscometer is placed in the bath. A small plumb bob, suspended in the support arm, is useful in securing vertical mounting of the viscometer. When the sample has become fluid, the vial is drawn upward until the pipet tip touches or nearly touches the bottom of the vial. A metal disk serves as a counterweight t o hold the vial in this position. When the sample and viscometer have attained bath temperature, the sample is sucked up into the pipet to the correct charging level and the vial is then lowered to the bottom of A , in which position the pipet tip will clear the top of the liquid in the vial after the contents of the pipet have been discharged, The time required to discharge the pipet can now be determined. Any number of repeat determinations can be made without dismantling the pipet, After the determinations the sample drains into the vial and is available for other uses with a minimum of loss. Results are reproducible to 0.2 per cent. If the dimensions of the capillary and bulb of the viscometers of this design are made t o correspond to those of the Ostwald-Fenske A. S. T. M. viscometers, these viscometers will be about twice as fast, owing to the larger head of liquid. These viscometers have a record of successful use in the author's own laboratory. Uncalibrated viscometers t o accommodate a screw-cap vial 8 cm. in length by 2 em. in diameter and wlth capillaries and bulbs of the same dimensions as the OstwaldFenske A. S. T. M. viscometers were obtained from the Scientific Glass Apparatus Company.
Literature Cited (1) Dean, E. W., Hill, H. H., Smith, N. A. C., and Jacobs, W. A., U. S.
Bur. Mines, Bull. 207, 45 (1922). (2) Mair, B. J., Schicktanz, S. T., and Rose, F. W., Jr., J. Research Natl. Bur. Standards, 15, 557-74 (1935). (3) Ruh, E. L., Walker, R. W., and Dean, E. W., IND.ENG.CHEX., ANAL.ED.,13, 347 (1941).
