PHOSPHORESCENT ZING SULFIDE 
 
 BY 
 
 AI>BERT H. BARNETT 
 
 THESIS 
 
 FOR THK 
 
 DEGREE O E B A G H E L O R O F S C I E N C E 
 
 IN 
 
 C H E M IC', A L E N G 1 N F. E R 1 N G 
 
 COl.LEGE OF LIBEHAF ARTS AND S(’1 !;nCFS 
 
 UNIVERSITY OF ILLINOIS 
 
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 THIS IS TO CERTIFY THAT THE THESIS PREPARED UNDER MY SUPERVISION BY 
 
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 ENTITLED _PIiOS?RPJlSSCFJL^:;i_ZJL:iI^ 
 
 IS APPROVED BY ME AS FULFILLING THIS PART OF THE REQUIREMENTS FOR THE 
 DEGREE OF BAAb-iiliir__af__SiLipj'2iie 1 e c h ? ni c .•-i. I i? 'rvc j r. e e r 1 
 
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 I Instructor in Charge 
 
 Approved 
 
 HEAD OF DEPARTMENT OF 
 
 60019^5 
 
Digitized by the Internet Archive 
 in 2016 
 
 https://archive.org/details/phosphorescentziOObarn 
 

 TABLE OF COFTSFTS. 
 
 PAGE. 
 
 I. HISTORIC:.! L. 
 
 II. EXPERIl.lEirTAL 
 
 1. Thermite Method 4. 
 
 2. MacBougall, TTright and Stewart 
 
 Method 4. 
 
 3. Hofmann and Dacca Method 8. 
 
 4. Modification Method 9. 
 
 III.CONCIU^'IOIIS 13. 
 
 BIBLIOGRAPHY 15. 
 
- 1 - 
 
 ACKNOWIEDGf®NT. 
 
 The writer v/ishes to express his very sincere 
 thnnJcs to Dr. B.S. Hopkins for his kindly criticism and 
 helpful suggestions rendered during the preparation of 
 this thesis. 
 

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1 . 
 
 PEOSPHORgSC'^lTT ZIImG STTIFIDE . 
 
 I. HT.^TOPTGAI 
 
 Many substances, ivhen eicposed to some source of 
 light such as the sun, possess the property of becoming 
 themselves self luminescent. That is, they will glow for 
 some time after the exciting source has been removed. 
 
 This very interesting phenomenon is knoivn as phosphores- 
 cence. If the period in which the bodies retain this light 
 is so short that it seems to disappear simultaneously with 
 the exciting medium, we have fluorescence. The difference, 
 then, between phosphorescence and fluorescence is merely 
 the length of time in which the light can be retained. One 
 of the strange features connected with this form of light 
 emission is that there is no apparent rise in tempera-ture 
 accompanying its production. 
 
 Por a great many years, no distinction v/as made be- 
 tween the glowing of phosphorus caused by the oxidation of 
 its vapors and phosphorescence. As a matter of fact, when- 
 ever the latter was found to exist it was attributed to the 
 
 1 
 
 prescence of the former element, in 1768, J. Canton heat- 
 ed a mixture of egg shells and sulfur and was surprised to 
 find that the product glov^red after exposure to sunlight. 
 
 His observations and experiments were published under the 
 heading, ‘ nn easy method of making a phosphorus that will 
 imbibe and emit light”. His product was later known as 
 
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 compound after excitation, a stronger phosphorescence was 
 
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 produced but of shorter duration. A few years later beebeek 
 discovered that short wave lengths produced the most intense 
 illumination when used for excitation and that red light 
 quenched the intensity. 
 
 The compounds that have been found to phosphoresce 
 with the greatest intensity are the sulfides of the alkali 
 earths, HaS, Gab, Srb and zinc sulfide. However, the liter- 
 ature on the subject is characterized by its contradictory 
 character and vagueness. in this work it was endeavored to 
 determine the best method of preparing phosphorescent zinc 
 sulfide and also to study the conditions that caused phos- 
 phorescence 
 
 In 1686, bidot^ prepared phosphorescent zinc sulfide 
 
 by heating the crystalline sulfide for 4-5 hours in an atmos- 
 
 4 
 
 phere of sulfur dioxide. Two years later, Verneuil discov- 
 ered that he could obtain a phosphorescent compound by heat- 
 ing precipitated zinc sulfide to redness in the preseence of 
 
 alkali chlorides or the sulfides of other metals. In 1699, 
 
 5 
 
 Moure lo found some natural zinc sulfide crystals v^hich 
 phos'-'horesced after exposure to light. This led to mi-ch 
 discussion as to the probable exi stance of pure phosphorescent 
 substances and just what impurities were necessary for its 
 production. 
 
 E3q)erlments conducted independently by Grune and 
 
 7 
 
 Hofmann & fiucca, in 1904, on methods of producing phosphor- 
 
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 escent zinc sulfide seemed to indicate that,- 
 
 1, The intensity of phosphorescence diminished with an 
 increase in purity, 
 
 S. 3mall traces of impurities such as magnesium and man- 
 ganese greatly increased the intensity of the phosphorescence. 
 
 3. The addition of some sodium chloride had a beneficial 
 effect. 
 
 4. Certain metals such as iron, cobalt and chromium 
 
 were detrimental to the production of phosphorescent compounds. 
 
 in a paper published in 1917 by Maci)ougall, v/right and 
 Stewart some of the above factors were verified and the quant- 
 ities of impurities necessary were determined. 
 
 Phosphorescence can be elicited by either magnesium ribbon, 
 sunlight, cathode rays, x-rays, mercury arc or an electric 
 globe. 
 
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 The following methods of preparing phosphorescent zinc 
 sulfide were investigated, - 
 
 1. Thermite Method. 
 
 2. iiacDougall, Wright and Etewart Method. 
 
 3. Hof mann and lihicca Method. 
 
 4. Modification Method. 
 
 1. TES:miTE MSTiiOH. 
 
 If a quantity of zinc dust and amorphous sulfur are 
 mixed in molecular proportions, that is 65 parts of zinc to 
 3E parts of sulfur by weight, and then heated, a very violent 
 reaction takes place and zinc sulfide is produced. If a small 
 amount of a metallic impurity is added to the mixture and the 
 operation repeated v/e have all the conditions necessary for 
 the production of a phosphorescent compound. Hov;ever, this 
 method proved unsucessful because a uniform product could not 
 be obtained. Eome of the sulfide glowed more intensely th^in 
 the rest. 
 
 2. MACHOTJGAIL, .>KIEHT aHJJ ETB.vAHT l^THOD. 
 
 Zinc chloride sticks were dissolved in water and the 
 solution was made alkaline, a considerable quantity of ferric 
 hydroxide precipitated so that the solution was allowed to 
 stand for 2 days in order to insure the complete removal of 
 iron because of its poisonous effect on the phosphorescence. 
 

 
 
 
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 i‘he solution was then filtered, diluted to molal, and 15 
 grams of sodium chloride were added per liter. 15 cc. of a 
 thousandth grsjn molecular solution of copper chloride was 
 added to 100 cc. of the zinc chloride and the zinc sulfide 
 was then precipitated with hydrogen sulfide. ‘i‘he precipitate 
 was filtered, dried at about 100° and ground in a porcelain 
 mortar. 
 
 The ease with ?/hich the samples are contaminated 
 cannot be overemphasized, .absorption of gases from the air, 
 dust, or contact with metallic objects have a very deleterious 
 effect. 
 
 later, it was found more practical to use about 500cc. 
 of zinc chloride at a time instead of lOOce. because comparative 
 results were not obtainable from different batches of stock 
 solution. One reason for this difference was the difficulty 
 in precipitating exactly the same amount of sulfide each time. 
 The best results were obtainable when about one-half of the 
 entire amount of sulfide was precipitated. If all of the sul- 
 fide was brought down the results were much inferior. Since 
 hydrogen sulfide was used for the precipitation, it was not 
 possible to bring down exactly one-half of the zinc each time. 
 Ammonium sulfide was tried but it gave inferior results. 
 
 The degree of phosphorescence was improved by sieving 
 the zinc sulfide thru silk, because of the danger and ease of 
 contamination, a metal sieve was not used. instead, the piece 
 of silk was placed between the wide ends of two large funnels. 
 
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 il’or heating the samples, a four inch muffle furnace 
 was found to be the most practical, it was modified by plac- 
 ing a well fitting clay plate as a false bottom, ^ust above 
 the gas jet, in order to keep the flames from the crucibles 
 as that would cause uneven heating, hy means of this arrange- 
 ment about six crucibles could be heated at the same time if 
 necessary. The samples were heated at various temperatures 
 in order to determine the affect of time and heat on phosphores- 
 cence. A pyrometer was used for the temperature measurements. 
 
 To determine v/hen the maxiniara phosphorescence was reach- 
 ed, samples were taken out every two minutes with a porcelain 
 spatula and tested immediately under sunlight, magnesium ribbon 
 or electric globe. A small bottomless cylinder with an obser- 
 vation aperture on the top was found very useful for daylight 
 testing. By means of this device the latter could be performed 
 in the vicinity of the furnace as it performed the function of 
 a dark room. 
 
 Porcelain crucibles were found to be the best although 
 not entirely satisfactory. They were fouifi to be attached by 
 
 the fumes evolved during the heating so that they could only 
 
 be used once. Metal orjicibles contaminated the product very 
 easily. The crucibles were kept loosely covered to prevent 
 eny contamination from the air and to allow the fumes to escape 
 slowly. 
 
 It was found that phosphorescent zinc sulfide is much 
 
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 more sensitive to heat treatment than the sulfides of the alkali 
 earths. In the case of the latter, excellent results were ob- 
 tainable between a wide range of temperatures and time inter- 
 vals. I'hat is, a sample could be heated at 850*^ for anywhere 
 from 15-25 minutes without any appreciable difference in the 
 degree of phosphorescence. On the other hand, if a sample of 
 zinc sulfide were heated at the s.ame temperature, between a 
 range of four minutes, the phosphorescence would pass from a 
 slight intensity through a maximum point and back to a low in- 
 tensity again. 
 
 The following three temperatures and their correspond- 
 ing time intervals were found to be the most practical, - 
 
 Temperature 
 
 Time 
 
 800° 
 
 15 min. 
 
 850° 
 
 12 min. 
 
 900° 
 
 10 rain. 
 
 A.t higher temperatures, the samples could not be 
 tested rapidly enough as the time interval decreases with an 
 increase in ten^^erature. At lov/er temperatures, the products 
 were found to be inferior. 
 
 The phosphorescence of zinc sulfide seems to be 
 more intense than that of the alkali earths but of a shorter 
 duration. 
 
 CRITICISM OP MACDOUGAII , ’/7RIGHT AITD STEWART METHOD. 
 
 1. The amount of sulfide precipitated could not be 
 accurately regiilated. It was found that the sulfides of cooper 
 
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 and manganese precipitated "before the ainc sulfide upon pass- 
 ing hydrogen sulfide into the solution so that the quantity of 
 impurity was not proportional to the amount of zinc sulfide 
 precipitated, consequently, duplication of results could only 
 be accomplished with the greatest difficulty. 
 
 2. fhe amount of sodium chloride contained in the samples 
 depended upon the amount of liquid adsorbed by the percipita-te 
 during filtration and consequently was a variable quantity. 
 
 3. i'he zinc chloride contained other impurities such as 
 cadmium and lead which were not removed by this method. 
 
 3. HOFMiVM AFD BUCCA TfflTHOB. 
 
 In this process, the zinc sulfide was precipitated from 
 zinc ammonium sulfate as the latter can be prepared in a very 
 pure state by recrystallization in water 
 
 20 grams of zinc ammonium sulfate, 5 grams of sodium 
 chloride and .4 gram of magnesirm chloride were dissolved in 
 460 cc. of distilled water which had been slightly acidified 
 with sulfuric acid. lOOcc. of ammonium hydroxide were then add- 
 ed, the solution was stirred thoroughly, and allov/ed to stand 
 for 24 hours. The precipitation, drying and heating were then 
 carried out as described in the above method. 
 
 GP.TTICISM OF HOFMm: AIID DFCCA MFtHOB. 
 
 1. The amount of sodium chloride varied as in the Mac- 
 Dougall Method. 
 
 2. Its use was limited to magnesium and manganese. 
 

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 I’his method might be considered as a combination of the 
 good points in the above two methods and those in Lenard and 
 Xlatt's method for the production of phosphorescent sulfides 
 of the alkali earths. 
 
 Zinc sulfate was used as a raw material instead of the 
 chloride because the chlorine affects the phosphorescence and 
 the amount of it was regulated in the last stages of this 
 procedure in order to be able to duplicate results. 
 
 50 grams of zinc sulfate were dissolved in about 450 cc. 
 of water, the solution was heated and then acidified with 5 cc. 
 of nitric acid, androgen sulfide was then passed in and the 
 solution f il tered, thus eliminating any cadmium or lead that 
 might be present. 
 
 ‘rhe hydrogen sulfide was prepared by passing electrolytic 
 hydrogen thru boiling sulfur. I’he electrolyte was a lO/o sodium 
 hydroxide solution and the electrodes of nickel gauze. The 
 sulfur was purified with carbon disulfide. The product formed 
 was very pure but the yield was small because of the ease with 
 which hydrogen sulfide decomposes at high temperatures. Later, 
 this method was discontiniied because the samples were not suf- 
 ficiently improved to v/arrant its substitution for the mu.ch 
 more simple and efficient method of using pyrites and sulfuric 
 acid in a kipp generator, in the latter method a purification 
 train was employed which consisted of two units containing 
 cotton, one of sulfuric acid and one of distilled water. 
 

 
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 The filtrate from the hj'drogen snlfide treatment 
 was treated with lOcc. of concentrated nitric acid and boiled 
 for ten minutes, 20c c. of ammonium hydroxide were then added 
 and the solution filtered, -mmonium hydroxide was then added 
 in excess until the precipitate which first formed redissolved. 
 The solution was allowed to stand for 48 hours and the ferric 
 hydroxide then removed by filtration. Hydrogen sulfide was 
 then passed into the warmed filtrate to saturation. The filter- 
 ed zinc sulfide was washed very thoroughly, this being the only 
 method in which that operation can be performed , j?‘inally, it 
 was crushed and sieved thru silk. 
 
 The impurities were introduced by placing lo cc. of 
 dry alcohol in a porcelain mortar. The active metals, such as 
 copper and manganese , were dissolved in water and the solution 
 diluted so that 1 cc. contained .001 gram of metal. By means 
 of a capillary tube the required pjnount of impurities was add- 
 ed to the alcohol. The flux, Bad, was then added in the dry 
 form and finally the zinc sulfide was introduced. The constit- 
 uents were thoroughly mixed by grinding until the alcohol had 
 entirely evaporated giving a dry product. 
 
 The heating was carried out by placing the porcelain 
 crucible containing the sulfide in a larger clay crucible and 
 putting a few crystals of sulfur between the two in order to 
 have a red'cing atmosphere. Both crucibles were covered secure- 
 ly thus preventing any oxidation of the sulfide. 
 
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 For a phosphorescent sample containing copper, the follow- 
 ing proportions were found to he the best,- 
 
 4 grams zinc sulfide, .5 gram sodium chloride, .0004 gram 
 copper. 
 
 For a phosphorescent sample containing mnganese, the 
 following proportions were used,- 
 
 4 grams zinc sulfide, .5 gram sodium chloride, .008 grcm 
 manganese. 
 
 Uranium, molybdenum and vanadium were also tried but the 
 results were inferior to those obtained from copper and man- 
 ganese. 
 
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 CCITCIFSIOITS. 
 
 The Modification Method was found to be best because it 
 removed all of the impurities in the raw material and also 
 gave restilts which could be duplicated at any time. A large 
 q uantity of pure zinc sulfide could be prepa,red as a stock 
 supply, which facilitated the rate at which samples could be 
 prepared. 
 
 The necessary constituents were found to be the pure 
 sulfide, an active metal and a medium or flux thru which the 
 tv/o were brought into intimate contact. 
 
 Upon heating a sample of zinc sulfide, a considerable 
 quantity of chlorides are driven off as fumes. If the sample 
 was heated longer than the time required for the production 
 of phosphorescence, it was found that the zinc sulfide was 
 almost entirely crystalline. This indicated that all of the 
 necessary impurities had been evolved as chlorides because 
 the latter prevent the crystalline formation due to their high 
 vapor pressure. 
 
 THSCHY. 
 
 The mechanism thru which phosphorescence is produced 
 seems to be a chemical union of the active metal with the sul- 
 fide causing a very complex, unstable molecular formation. 
 
 One molecule of Copper, for example, unites with a great number 
 of zinc sulfide molecules. On the application of pressure 
 as in grinding, the phosphorescence diminishes. due to a dis- 
 turbance of the unstable complexity. The excitation by means 
 
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- 14 - 
 
 of light might cause electronic vibrations in the sulfide 
 which continue for some time after the excitation censes. The 
 wave length of these vibrations must be within the visible 
 spectrum in order to produce phosphorescence. The frequency 
 c.an be changed by temperature variations so that a sample which 
 phosphoresces at ordinary temper.atures will not do so if the 
 latter is increased or diminished sufficiently to bring the 
 vibrations beyond the visible spectrum. 
 
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-15- 
 
 BIBIIOGRIPEY. 
 
 1. — — Phil. Trans. ^ (257-344) 1768 
 
 2 . Gothes Parhen. ( 3£3 ) 
 
 3. Compt. rend. 103 ( 188 ) 1886 
 
 4 . ibid 106 (1104 ) 1888 
 
 5 . ibid 1^ 1899 
 
 6 Berichte ^ (3076 ) 1904 
 
 7. ibid 37 (3407 ) 1904 
 
 Handbnch der Spectroscopie H. Kayser. 
 
 Phosphorescent Zinc Sulfide R. Tomeschek. 
 
 Ann. Physikj^ ( '189 ) 1921 
 
 Phosphorescent Zinc Sulfide MacBougall,etc. 
 
 Jour. Chem. Soc. Ill (663) 1917 
 
 Phosphorescenz lenard and Zlatt. 
 
 Ann. Physik (1899-1915)