US2802391A - Colorimeter - Google Patents

Description

F. J. MA IER COLORIMETER Aug. 13, 1957 2 Sheets-Sheet 1 Filed Feb. 29. 19,56

ATTORNEY United States Patent 2,802,391 COLORIMETER Franz J. Maier, Chevy Chase, Md., assignor to the United States of America as represented by the Secretary of the Army Application February 29, 1956, Serial No. 568,684

3 Claims. (CI. 88-14) (Granted under Title 35, U. S. Code (1952), see. 266) The invention described herein, if patented, may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to colorimeters. Colorimeters are instruments used to compare the absorbing capacity of an unknown (the color of a system of unknown concentration) with that of a standard (the color of a system of known concentration or color value). In general and within certain defined limits, the sensitivity of such visual instruments is a function of the length of the light path through the colored mediums; the longer this path, the more sensitive the system becomes to slight changes in the concentrations of the unknowns. Instruments are available providing permanent color standards corresponding to definite concentrations of substances contained in samples of a large variety of materials. Among such instruments available for the analysis of liquids, those providing the longer light paths are almost invariably more expensive than those provided with shorter or smaller tubes. In efforts. to economize, many laboratories are provided with the less expensive equipment with an attendant sacrifice of accuracy and uniformity of results. One purpose of this invention is to provide an instrument incorporating the accuracy obtainable generally only with those devices designed for the longer tubes combined with the simplicity of housing and construction associated with the less expensive and more generally available laboratory equipment.

The present invention provides an inexpensive, accurate, easily handled colorimeter which is adaptable for examination of a wide variety of solutions, suspensions, etc., by merely changing the tube contents and by substituting, if necessary, appropriate color standards. The invention combines Nessler-type tubes, preferably 100 ml. glass tubes, supported in a row in an inexpensive rack of the simplest construction, an attachment providing permanent color standards, an optical system usable with almost any light source, and means slidably supporting the dial-like attachment and the optical system on said rack, so that the operator working in the proper light may have a clear view lengthwise through any selected one of the row of Nessler-type tubes and may visually compare its solution with the permanent color standards, then may slide the device along the rack for an examination of the solution in another tube in the same row. The invention also provides a tube rack attachment which may be removed from one rack and placed on another of like construction for a different series of examinations. The tubes on each rack need not be disturbed when the attachment is so removed.

In the accompanying drawings showing a preferred embodiment of the invention,

Fig. 1 is a perspective view of the complete apparatus;

Fig. 2 is'a vertical central cross section, on a larger scale;

Fig. 3 is an enlarged fragmentary plan view showing the eyepiece, the light shield, a few of the Nessler tubes and a portion of the rack;

Fig. 4 is a vertical section on line 44 of Fig. 3, onntting the lower portions of the tubes and rack;

Fig. 5 is a vertical section on line 5-5 of Fig. 3, also omitting most of the rack;

Fig. 6 is a plan view of the light shield and holder, showing in dotted and full lines the color standards dial directly below;

Fig. 7 is a plan view showing the color standards dial and its support;

Fig. 8 is an enlarged section on line 88 of Fig. 7;

Fig. 9 is a plan view of the holder for the light shield and color standards dial;

Fig. 10 is an enlarged (full size) section on line 10-10 of Fig. 4;

Fig. 11 is an enlarged (full size) section on line 11-11 of Fig. 5; and

Fig. 12 is an exploded perspective view showing the elements of the optical system of Figs. 10 and 11.

Referring particularly to the drawings, the device includes a rack 15 for supporting a set of Nessler tubes 16, a reflector 17 for reflecting light from any convenient light source up through the tubes lengthwise, a sliding support 18 movable along the rack over the upper ends of the tubes, and an optical assembly 19, a light shield 20 and a color standards dial 21 all mounted on, but removable from, the sliding support. The tube rack 15 supports a mirror or brightly polished metal reflector 17 between its legs 22, 23, said reflector being set preferably at an angle of about 45 to the horizontal. If preferred,

. the reflector may be mounted on pivot pins to turn about a horizontal axis and may be clamped by thumbscrews or nuts in the preferred angular position, so as most effectively to catch the beam of light from the light source (not shown) and reflect it up through the tubes. Obviously the light source may be a window, preferably a north-facing window, or it may be an incandescent lamp or fluorescent tube located at any convenient point. The rack has a perforated or apertured shelf 24 for supporting the lower ends of the Nessler-type tubes and another upper shelf 25 provided with apertures 26 which are large enough to receive the tubes freely, so that the tubes are easily inserted and withdrawn through apertures 26. Light which impinges on the reflector is reflected through apertures 27 in shelf 24 and passes through the tubes and their contents longitudinally (vertically) to the optical system at the top of the rack.

Slidable on upper shelf 25 is a support 18 which straddles the upper ends of the tubes as shown in Figs. 1 and 2, having a shape something like an inverted U, with two parallel vertical side plates 28, 29 and a horizontal top plate 30 secured to the upper edges of the side plates. The side plates 28, 29 are preferably trapezoidal, with their lower edges longer than their upper edges, and on the inside near their lower edges the side plates carry straight ribs or flanges 31, 32 which rest on the upper shelf 25 and permit sliding of support 18 thereon. Greater stability is insured by placing ribs 31, 32 near the lower, wider edges of side plates 28, 29 and by having the inner surfaces of said plates make sliding contact with the edges of the shelf 25. Top plate 30 has an aperture 33 for light to pass through from the Nessler-type tube (whose contents are being examined) to the optical system above. A thin metal ring 34 is set in a narrow annular groove cut in top plate 30, as shown in Fig. 8, and color standards dial 21 is supported on the upper edge of the metal ring so as to be rotatable manually by the operator. Top plate 30 also has a large light aperture 34 and a pair of dowel holes 35 for receiving dowel pins 36projecting downwardly from the light shield or hood 20, so that the hood is supported on the top plate.

Dowel pins 36 and a raised strip 37 (Figs. 4 and 9). projecting above the upper face of the top plate will support the hood firmly yet will permit easy removal. As Fig.

4-shows,- ,.t:he:hood is spaced slightly fr'omthe rotatable dial 2.1 to permit free turning of the dial Without: rubbing against the: hood. Similar arrangements can be made for supporting permanent color. assemblies.

Hood Zii ispreferably ofv metal finishediin' a. dull black to minimize light reflections. bottom plate 38, having apertures 39, 4t] and 41, also having apair of sockets'42. (Fig. 6) locatedcentrally for receiving dowel pins 43, 44 on the optical system assembly 19 to-be; described. See Figs. and 10. Hood 2%) is open on one side and closed on the other three sides and its side which is opposite the open. side is higher, so as to-shield the eye. of the observer. from the light source, which is beyond the highside 45..

The. optical system assembly (Figs. 10, 1.1 and 12) includes an eyepiece 46, a lens 47, a casing 48, a pair of prisms 49, 50 forming a prism unit, a. panel of clear glass 51, a locking bar 52, and the previously mentioned pair of dowel pins 43, 44; Said dowel pins are screwthreaded on their inner ends and are passed through perforations in the locking. bar 52 and: are screwed into tapped bores 53, 54 provided in the lower end of casing 48. This entire optical assembly is available on the market and per se forms no part of my invention. The prisms 49, 59 are similar to the prisms shown in the Bulkley Patent No. 2,684,010. dated July 10, 1954, and act in the same Way. Eyepiece 46 and casing 48 may be of black Bakelite or a. similar dark resinous plastic. Lens47 is a weakly magnifying. lens and may be replaced by a more powerful lens by merely slipping off the frictionally held eyepiece.

The color standards dial 21 is an article of commerce and needs only a general description. Other permanent color standard assemblies may be. used in lieu of it. Dial 21 is so supported that one side of it projects beyond the sliding support 18, as shown in Fig. 3, so that the operator may turn it easily. It has a round fiat. shape very much like a telephone dial, is made of Bakelite or similar resinous plastic colored black,.andv hastransparent tinted glass or plastic filter disks 64} arranged in a circular series around the center of the dial. These filter disks are accurately made and are of graduated tints andare identified by insignia such as those shown. at 61 in Fig. 7. Each insigne. appears in turn at the aperture 41, Fig. 6, as the dial is rotated, and it identifies. the. filter disk appearing through. aperture 49. The insignia illustrated in Fig. 7 are digits running from 0 to 1.6, but could beletters or even symbols; their number is the same as-the number of the filter disks which they identify. The upper shelf 25 may have labels or stickers (not shown) adhered to it to permit identifying each tube on the rack, or the tubes themselves may be identified by labels in the event their solutions are to be preserved for future reference. Each of the filter disks is held in its socket 62 by a locking ring 63 andfis removable, hence is replaceable by another filter disk. If this is done, the insignia will of course be changed to correspond. As shown in Fig. 8, the color standards dial has a circular socket 64 co-axial with the dial, said. socket 64 being open at the bottom to receive the thin circular edge of bearing ring 34. Socket 64 is formed by thecentral hub 65 and a ring 66 locked inside the hub (see also Fig, 7) and spaced therefrom. Ring 66' supports aclear glass disk 67 in the exact center of the dial through which light fromv one of the tubes and contents below passes to the optical system located above, as described in theforegoing. It will be clear that the dial 21 may be lifted: off its bearing ring 34 by first lifting the shield or hood 2%, and another color standards dial with different filter disks may be substituted for the one previously in use, or a differently shaped andconstructed color standard holder may be used. Such a substitution or. changemay. be madewhen changingfrom. one class'of Hood includes: a flat.

solutions to another, e. g., from blood solutions to syrup solutions.

As will now be clear to those skilled in the art, the apparatus of the invention makes it easy for an operator to get a series of readings giving the color values of diiferent solutions or suspension's ina-series of tubes supported in the rack. Each inspection involves two tubes placed side by side in the rack; usually the same solution or dispersion. (the one. to: be examined.) will be. poured intoeach pair of tubes 16, and areagent is thenadded tothe tube that is under the central aperture 34a. The'sliding support 18 is placed by the-operatorover the'pair of tubes to be inspected and with light from the light source passing upwardly through both tubes, one beam of light travels through a tube 16 containing: the. solution orv dispersion, thence through perforation 33, through one of the filter disks as selected by the operator, and through the optical assembly" 19, while; a second beam of light after traversing the second. tube (to which. the reagent has been .added') travels.throughperforation 34a, through the clear glass disk 67 at the center of thedial, and through the optical system. The. two beams ofv light are brought together because of the prisms 49, 50, and a single elliptical image which is a composite of the two, will be seen in the eyepiece. This. is shown in. Fig.3. As one of the pencils of light passes through a filter disk, While the other passes through the tube and its contents then through glass. disk 67, the color of one-half the elliptical image will be a projection. of the particular filter disk then in the. optical system (as determined by the operator, who rotates disk 21) while the color of the other half of the elliptical. image will be the. color of the tube and its contents. The operator will rotatethe dial until he sees that the two-images are of the. same tint or color, then he will make a notation of the reading given by the insigne 61' which then. appears in aperture 41. Other readings are obtainable from other tubes-by merely sliding support 13 along the rack. As-previously pointed out, support 18 may be moved to another rack, or a new set of tubes may be placed in theira'ck for. anew set. of readings.v

A number of changes may be. made in the described construction without departing fromthe invention. Thus the rack could be circular or arcuate, and the slidable support could be adapted to move as freely over such a rack. The optical system. does not have to include a mirror or'refiector in the base of. the rack, since asource of light (such as a fluorescent tube) might be placed in the lower part of'th'e rack, with the. necessary shielding to confine the light emitted. to pencils of light reaching to tubes and the filter disks prior to entering the optical system; therefore I employ the. term source of. light in its broad sense to include a reflector which acts as a sourcev of light by reflecting light rays but does not emanate or generate light rays. The optical unit may be superseded by other units of different construction.

What I claim is:

1. An optical'comparator or colorimeter comprising, in combination; a rack for Nessler-type tubes having two horizontal shelves arranged one above the other and a pair of legs supporting the shelves; the lower shelf being perforated at intervals to permit light to pass therethrough from below and having seats for Nessler-type tubes surrounding said perforations so that beams of light may pass lengthwise through such tubes and their contents when such tubes rest on said seats; the upper shelf. having apertures through which such tubes when so seated may extend; a' support having two light-passing apertures and having means fixed thereon slidably supporting it on the upper surface of said upper shelf, said support straddling the upper ends of said seated tubes; an optical assembly carried on said support and including a prism unit for gathering light beams passing through two apertures' in said support, and an eye piece receiving light beams from the prism unit; a color standards dial rotatably and removably supported on said support beneath said optical assembly but above the light-passing apertures and adapted to receive two beams of light passing through two adjacent tubes seated as aforesaid and adapted to transmit said beams to the prism unit and/ eye piece of the optical assembly, so that the eye of the operator placed at the eye piece may see two images side by side of the contents of two adjacent tubes seated asaforesaid. 2. The invention defined in claim 1, wherein the slidable support comprises a perforated upper plate, two side plates fixed at their upper edges to said upper plate and lying in vertical planes, a straight rib fixed to each side plate on the inside near its lower edge, said ribs together supporting the slidable support by direct sliding contact with the upper surface of the upper self, said slidable support having its side plates extending below and being substantially in contact with the upper shelf on both side edges.

3. A portable assembly useful for making color comparisons comprising a rigid support having the general shape of an inverted U having two legs each provided with means slidably engageable with a horizontal shelf of a Nessler tube rack, said support also including a horizontal member to which the upper ends of the legs are secured; said horizontal member being perforated at two points to permit two generally vertical beams of light to pass therethrough; a circular color standards dial having a circular series of filter disks of difierent color values and a central transparent disk; the distance apart of the perforations in said horizontal member being the same as the radial distance between the filter disks and the central transparent disk; means supporting said color standards dial rotatably and removably on said horizontal member, so that the color standards disks may be moved seriatim over one of said two perforations, the central transparent disk of said dial being above the other of said two perforations; and an optical assembly including an eye piece, a lens and light collecting prisms mounted on said support above the color standards dial; the entire assembly being movable over the upper ends of a series of Nessler tubes supported vertically on a rack, so that color comparisons may be made of illuminated solutions or dispersions in two adjacent tubes of said series at one time.

References Cited in the file of this patent UNITED STATES PATENTS 1,976,672 Peet Oct. 9, 1934 2,007,087 Hird July 2, 1935 FOREIGN PATENTS 818,270 Germany Oct. 25, 1951 OTHER REFERENCES Optical Methods of Chemical Analysis by Gibb, Jr., published by McGraw-I-Iill Book 00., New York, 1942, pages 131433.

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