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T H E J O U R N A L OF I X D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
Vol. 9, NO. 8
I
ORIGINAL PAPERS ART OF COLORING GLASS By H. ROSENTHAL
A number of writers have recorded t h e beautiful tints a n d colors t h a t some glass assumes when exposed t o sun a n d weather, particularly mentioning t h a t among t h e fragments of glass found in t h e ruins of some of t h e eastern countries pieces of almost solid turquois-blue were discovered and t h e glass windows of old homes a n d parts of glass bits a t t h e seashore were tinted with these beautiful colors.* Thomas Garfield3 quotes a series of experiments covering t h e coloring of glass b y t h e action of t h e sunlight upon glass. Lillman’s American Journal4 and t h e Journal of the Society of Arts5 mention glass turned gold color a n d also glass turned t o purple.6 This reference was made b y Dr. Faraday in t h e Chemical Research, 189, page 142. Pelorge’ states t h a t all glass is changed b y t h e action of t h e sun, tests being made by covering p a r t of t h e glass with paint a n d exposing for several years t o t h e sun’s action under various conditions; when t h e paint was removed, t h e result was varying depth of color on t h e same piece of glass. Of glass examined for color or examined edgewise, t h e tints which some of t h e glass assumed varied from greenish, yellowish, blue-green, brown, yellow t o deep purple. The report also states very definitely t h a t optical glass was exposed for a period of two years t o t h e sun without any noticeable change. B u t t h e suggestion was made t h a t if this could be exposed for a longer length of time, some reaction could be looked for. An interesting point is brought out b y one of t h e observers, v i z . , t h a t photographers experience a noticeable change in their time of exposure when taking photographs under skylights. As t h e glass in t h e skylight becomes old, anything from one year or more, t h e time of exposure has t o be increased, and experiments along this line show t h a t t h e change of color in t h e skylight glass absorbs a n appreciable amount of t h e actinic rays which can be easily substantiated by examining t h e spectrograms of t h e purple lenses. PURPOSE
OF THE PAPER
This paper describes experimental work done in t h e a r t of coloring glass b y artificially produced short wave lengths of light using t h e ordinary quartz mercury arc, a n X-ray tube, t h e Coolidge X-ray tube, a n d t h e n a special X-ray t u b e for producing negative electrons. I n order t o show t h e position of t h e rays “termed” short wave lengths of light, Fig. I is presented. The 1 Presented a t the regular meeting of the New York Section of the American Chemical Society, Chemists’ Club, S e w York City, June 8, 1917. 2 Fox, PhiIa., Crookes, England. a Philosophical Magazine, 4 series, 8 6 7 , July t o December issue. 4 September and November, 1867. 5 February 1854. 6 This reference was made by D r Faraday in the Chemtral Research, 1859, page 142. Comples rendus. January, 1867.
chart indicates t h e wave lengths of radiations ranging from t h e visible part of t h e spectrum t o X-rays a n d t h e gamma rays of radium.
FIG.I-CHART
SHOWING WAVE LENGTHS
OF
RADIATIONS
The numbers across t h e t o p give their respective wave lengths in Angstrom units. The Angstrom unit is equivalent t o 1 0 - l ~ meter. The numbers immediately below represent t h e number of octaves which these rays range over. The region of about six octaves, beginning a t 4 and ending a t I O , represents t h e unmapped portion. This separates t h e extreme ultraviolet from t h e commencement of t h e very soft X-rays. T h e most easily absorbed X-rays, whose wave length has been determined, are t h e characteristic rays of aluminum with a wave length of 8 . 4 h;. u. Passing up through several octaves of X-rays, t h e limit indicated by t h e line “N” is reached; these represent the hardest, i . e., t h e most penetrating X-rays, which have so far been produced. The line “ M ” represents t h e medium penetrating ray. I t will be noticed t h a t some of t h e gamma rays, as produced by t h e disintegration of t h e radium atom, are of longer wave lengths t h a n some of t h e shorter X-rays. D a t a discussed in this paper were obtained a t t h e writer’s laboratory a t Camden, N. J., several years previous t o t h e granting of patent, and since then, through t h e courtesy of Dr. Coolidge and Dr. Whitney of t h e Research Laboratory of t h e General Electric Company a n d D r . Luckiesh, of t h e Nela Research Laboratories; also some records were made b y t h e Bureau of Standards, Washington, including some assistance given by Drs. Fisher a n d H u t t o n , of Philadelphia, t h e object of which is t o show what has been done with t h e method of coloring glass and what are some other characteristics of t h e glass so colored. HISTORY
O F DEVELOPMEKT
The first experiments, about eight years ago, were carried on with an ordinary X-ray tube a n d induction coil and the faint color of t h e glass was noticed after about two days’ treatment. As t h e designs of t h e high tension apparatus were improved t h e period of treatment was very much lessened. I n t h e meantime experiments were also made with other sources of rays, such as t h e incandescent burner and t h e quartz mercury arc, b u t it was not until the development of t h e special water-cooled, self-rectifying tube b y Dr. Coolidge t h a t i t was possible t o obtain t h e needed energy for producing results in a definite way. The term color has been used t o designate the tint or kind of hue white glass assumed after treatment,
T H E J O U R N A L O F I N D U S T R I A L .AND E N G I N E E R I N G C H E M I S T R Y
Aug., 1 9 1 7
a n d depth of color is used t o denote t o what degree this hue or t i n t has been carried compared with white glass, gauging t h e color from t h e surface nearest t o exposure t o rays. I n this paper t h e coloring of thin glass has been kept in mind which assumes t h a t we obtain a n even t i n t throughout t h e glass, but if thick glass is treated (over in.) t h e depth of color is pronounced, being deeper near t h e exposed side and gradually shading off. T h e present investigation has been carried on with the most recently developed electrical apparatus and on standard glass, no attention a t this time being paid t o investigating t h e field of various glass compositions or t o increasing t h e energy used in treatment of the glass. DESCRIPTION O F APPARATUS
The vacuum tube (Fig. 11) was about 4 inches in diameter with a n anode terminal of solid tungsten metal supported on a rod of molybdenum and a cathode consisting of a tungsten spiral which can be electrically heated.
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By controlling t h e penetration of t h e rays of t h e t u b e by varying t h e voltage, different degrees of color can be obtained. For example, in coloring a n extreme double concave lens as Fig. 111, i t is possible t o color it as marked b y t h e heavy line, so t h a t in looking through it, t h e effect of even tint will be received, thereby giving t h e effect which could not be produced in coloring glass. Inasmuch as i t is easier t o grind
lenses of this character from stock, material is usually taken from t h e ordinary flat glass t o begin with and as it is ground away t o t h e desired curve t h e thick portion will be dark and t h e thin light, t h e well-known result as shown in Fig. IV. ACCURACY O F DATA
Current measurements were made with standard measuring instruments. The spectrophotometric curves were made from readings with spectrophotometer and t h e spectrograms with quartz prismatic spectroscope on Cramer spectrum plates. MEANS I N SCOPE O F PRESENT INVESTIGATION
This method opens up a new a r t in t h e coloring of glass and analogous substances. I n t h e treatment of white glass for optical a n d scientific purposes peculiar photometric and spectroscopic, spectrophotometric results can be obtained. Fig. V illustrates t h e spectrophotometric curves of amber and amethyst glass made from glass chemically colored and compared with glass colored by this process.* “CROSS-FIRE
AND COIVNECmffs The vacuum of this bulb remains constant a t all times, t h e penetration of t h e t u b e being governed by t h e heat of t h e cathode spiral, and unless t h e filamant is heated t h e t u b e shows no conductivity in either direction, even with voltage as high as I O O , O O O volts. T h e t u b e suppresses any current in t h e direction which does not make t h e hot filament cathode. I t therefore is capable of rectifying its own current when supplied from an alternating source. I n order t o make this condition stable, t h e anode was watercooled, a n d t h e glass was kept from overheating by being cooled b y compressed air. The amount of electrons sent out by t h e tube depends on t h e temperature of t h e filament. Increasing t h e voltage on t h e terminals increases t h e penetration of t h e rays. The t u b e can be operated continuously without exhibiting any appreciable change in characteristics. The typical schedule for coloring optical lenses is as follows: TREATMEXT
RESULT Light color Medium color Dark color ( C ) 100 hl. A,, 50 Kv., 10 min. M . A . = Milliamperes. K v . = Kilo volts. (A)
100 hl. A , ,
50 Kv.,
(B) 100 M . A,, 50 Kv.,
2 min.
4 min.
THEORY”
I n Roentgen-ray therapy where t h e rays are wanted for t h e treatment of t h e deeper parts of t h e body, t h e cross-fire theory is made use of. This method is used t o minimize t h e ray action on t h e skin and superficial parts b y selecting different ports of entry for t h e radiation, t h e theory being t h a t if a n organ is exposed from several directions instead of from one direction, only, then i t receives several times t h a t quantity of rays which it would receive if exposed in one direction only and t h e skin is only struck b y t h e ray quantity emitted h o m t h e tube in one of t h e various positions. This theory was proven in t h e following manner: A cube of glass with 2-in. square face was subjected t o t h e cross-fire theory. A side was “rayed” by a beam 1,’2 in. in diameter. The glass side nearest, t h e t u b e was colored darkest and shaded off towards t h e center, and as each of t h e eight sides were rayed we found in t h e center of t h e cube a small cubical spot, equal in color t o any one of t h e outside surfaces. 1 Optical wedges can be made b y this method, and in the samples o 1 colored glass on exhibit, there was one wedge made in arithmetic steps. In coloring porcelain teeth, the coloring was made geometrical by placing a wedge of aluminum on the tooth. Designs and figures made by stencils allow coloring of porcelain ware. Semi-precious stones are changed in color, and some specimens of Kunzite shown were changed in a few minutes from their characteristic amethyst color t o an emerald-green.
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
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Vol. 9, No. 8
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comfort and strain. The white optical glass, after being colored by this process, has t h e same qualities and characteristics and is capable of performing t h e same functions as t h e original clear glass tinted or colored by t h e slow action of t h e sunlight extending over many years. The colors obtained were amethyst, amber, green a n d yellow tints. I n using this method in connection with optical lenses a n almost ideal condition exists, vis., in using the finished white optical lenses, which are made of t h e best glass obtainabie, a n d then coloring it, we obtain a glass which has characteristics valuable t o t h e oculist, i t long being known t h a t when eye-glass lenses are made of t h e sun-tinted glass, t h a t such lenses would shade the eyes of the person wearing them from the actinic ray of t h e spectrum and in cases of hypersensitive retina, t h a t different persons require lenses tinted t o different degrees of density, in accordance with t h e degree of retinal irritation. A glass may be of proper color t o alter t h e light which we wish t o allow t o enter t h e eye and yet have a transmission coefficient much lower t h a n t h e theoretically ideal glass. In chemically coloring glass t h e tendency is always toward black, so t h a t a glass might correspond t o t h e ideal glass combined with a smoked glass. There is, therefore, t h e problem of transparency besides t h e purely spectral problem, and you will note t h a t t h e spectrophotometric curves shown of glass colored by this method have a high degree of trans-
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T h e coloring of t h e glass follows t h e law t h a t "the work done by any force varies with the time through which it acts." X-light follows t h e law t h a t t h e work done by a given light varies inversely a s t h e square of the distance from t h e source of light. This gives us t h e simple formula, W = S / D z , in which E' is t h e work done, D t h e unit distance, and S t h e time of exposure. The next principle involved is t h a t work done by X-light varies with t h e quantity of current (C) passing through t h e tube, other conditions remaining constant, whence W = C S / D z . Another factor determining the work done is t h e penetration of t h e tube. This factor was checked by Prof. Wehnelt, t h e proof of which gives us t h e combined formulas, W = S C P ' / D z , a n expression
A W , 1917
T H E J O U R N A L O F I N D U S T R I A L AlVD EATGIA7EERING C H E M I S T R Y
of t h e work done b y X-light, using a t u b e of unit dimension, P being t h e penetration as measured on a Wehnelt penetrometer. Using a slide rule covering t h e equation DZTZ
x
D
= >-
c PZ
P = Wehnelt penetrometer readings target a n d glass X = exposure in seconds T = thickness of glass C = current measured in milliamperes = distance in inches between
we have a formula based upon a hypothetical unit of light which one can vary t o produce with exactness a n y desired result. Each make of glass, of course, has its own rate of speed of change by which t h e r a l u e X must be multiplied. T H E O R Y OF O P E R A T I O N
The coloring of purple glass is undoubtedly due t o manganese, yet t h e color of this glass is not exactly t h e same as in t h e manganese specimens, which have been tested. This, of course, can possibly be accounted for in several ways, such as t h e difference in t h e chemical substance of t h e glasses, or due t o t h e oxidation of t h e manganese, which may be different as obtained b y radiant energy t h a n b y t h e regular glass manufacturing process. T h e other colors obtainable, very likely follow along t h e same lines, b u t i t is also hard t o believe t h a t anything else b u t a direct physical change in t h e material, or a direct molecular rearrangement has taken place. Considering t h a t b y t h e application of heat, molecules can be rearranged, t h e action would appear, if taken synthetically, more naturally physical t h a n chemical. S Z; M MA R P
I-White glass turns t o different colors under this method. 11-Knowing t h e composition of t h e white glass, t h e color can be predetermined. 111-The depth of coloring of t h e glass is dependent on penetration of t h e rays, h e w e controllable. IV-The action is molecular a n d not confined t o t h e surface of t h e glass and t h e color is in and through t h e glass itself. Y-The action is reversible. VI-In coloring glass by t h e above-described method, results can be obtained which are not possible with glass colored by chemicals. VII-Other analogous substances, such as porcelain, quartz, and some of t h e precious and semi-precious stones, particularly those colored by manganese, respond t o this method of treatment. . The writer of this article makes no pretense t o accurate scientific knowledge, b u t gives t h e results of his observations and methodical experiments with t h e well-known phenomenon in t h e hope t h a t they may add some mite t o t h e s u m of human knowledge and may stimulate those who are better versed in scientific studies t o ascertain t h e exact cause and operations of this interesting power of t h e short wave lengths of light. ROSENTAAL ELECTRICAL LABORATORY CAMDEN,
N E W JERSEY
737
THE CHEMICAL CONTROL OF AMMONIA OXIDATION By PAULJ. Fox Received June 21. 1917
I n t h e oxidation of ammonia t o produce nitrous or nitric acid, t h e ammonia, mixed with air, is passed over a catalyzer heated t o a red heat. The ammonia content t o t h e air-ammonia mixture is given either b y running t h e air through aqueous ammonia or by mixing t h e ammonia gas with air. When t h e ammonia content is obtained by passing t h e air through aqueous ammonia, t h e mixture, of course, is saturated with water vapor a t t h e given temperature. I n t h e operation of this process, either on a n experimental or manufacturing scale, one of t h e most pressing problems is t h e chemical control, for on i t depends t h e accurate adjustment of t h e factors necessary t o t h e efficiency of t h e plant. I n fact in starting a new commercial unit, or getting d a t a on a design of furnace, or merely in testing a new catalyzer, especially over any period of time, t h e principal practical issue is finding out exactly what t h e chemical performace is under the various conditions (temperature and character of catalyzer, speed and composition of ammonia-air mixture, etc.). The chemical control naturally falls into four parts: ( I ) t h e examination of t h e gas before passing to t h e catalyzer, and (Z:I after coming from t h e catalyzer, (3) t h e working up of t h e results, and (4) t h e determination of nitrous acid. For t h e determination of t h e fairly high content' of ammonia in t h e entering gas, t h e ordinary gas analysis methods with mercury as confining liquid are applicable or t h e ammonia may be absorbed in standard acid and titrated. -4 thorough discussion of t h e various absorbing arrangements will be found in a paper by Edwards2 on t h e absorption of ammonia in illuminating gas. The method by absorbing in standard acid has t h e advantage t h a t a much larger sample can be used-in fact a continuous sample can be taken-and t h a t no mercury is required. T o test t h e Cumming absorber, t h e writer ran 1000 cc,of I O per cent ammoniagas through one like t h a t figured by Edwards, another absorber being connected in series beyond it. S o t a trace of ammonia passed into t h e second absorber, showing t h a t one is sufficient t o collect all t h e ammonia. It has occurred t o t h e writer that with this type of absorber it is possible t o determine t h e ammonia without making any titration. This is done by putting in a measured quantity of standard acid, coloring with an indicator and bubbling through t h e ammoniaair mixture, until t h e color turns. If t h e gas has been collected in an aspirating bottle, t h e volume corresponding t o t h e quantity of standard acid used is known, a n d the per cent of ammonia in t h e original mixture can be easily computed. T h e reason why this is possible is t h a t in t h e Cumming absorber there is a fair circulation, and with a little practice i t is not difficult t o hit t h e turning point, as t h e liquid is always approximately of t h e same composition. At t h e same time, t h e appearance serves warning as t o when t h e change will occur. 1 T h e theoretical air-ammonia mixture (dry) contains 14.33 per cent of ammonia. 2 J. D. Edwards, Bureau of Standards, Technologic Paper, 34 (1914).
