isa-normaladvance-1913-00087

Description:	THE NOEMAL ADVANCE87in that it appears green when looked at, buta beautiful, pure yellow when looked through.At first this peculiarity was attributed to thefact that iron is usually present in commercialuranium, but this theory has been exploded,because when almost pure uranium was used,the phenomenon was even more strikinglybeautiful than with the impure article. Soevidently this property belongs to the uraniumitself. The glass is made by the addition oftwo and one-half to three per cent of uranateof potash or ammonia to a potash-lime glass,free from lead. A green shade is obtained byadding .25 per cent of yellow uranate and twoper cent of copper oxide.Orange colored glass is obtained in twoways—by adding two per cent of ferric oxideand two-thirds per cent of manganese dioxide,and by the use of peroxide of iron withchloride of silver.Red glass is obtained by using either of thetwo metals, copper and gold. Copper is moregenerally used, and its use dates back manyhundreds of years, even before the timeof Christ. The beautiful shades of red inthe stained glass windows of the Old AVorld,which are so much admired, were producedby copper, although the exact formulas havebeen lost in many cases. Sub-oxide of copperis used, and great care must be taken that itdoes not unite with an additional, supply ofoxygen, for if this occurs, green and not redglass is produced. To prevent this oxidation,a little metallic iron is added, which causesslight reduction. Here is another danger, forif the reduction is great, a red-brown color isthe result. The glass, after the first heating,when taken from the crucible is nearly colorless, or with a slight green tinge. However,when reheated, a fine red appears. Thischange is believed by some to be due to achange in the molecular arrangement of theparticles. H. Rose supposes that a colorlessneutral or acid silicate of the sub-oxide ofcopper is formed at a high temperature, andthat when the glass is remelted at a lowertemperature this compound is decomposed anda portion of the sub-oxide separated. Suboxide of copper possesses such an intense coloring power that a small quantity even, is almost impermeable to light, so in coloring glasswith it, it is customary merely to flash colorlessglass with it—that is, to spread a thin film ofit over colorless glass.AVhen gold is used instead of copper, a particularly fine shade of ruby, or carmine, is obtained. Like copper red, the gold red is notobtained at the first heating. The mixture ismade differently from copper mixture, as thecopper is put in with all the other ingredients,and the gold is mixed with the sand alone. Avery dilute solution of gold chloride is used.It is thoroughly mixed with the sand and thendried. The other constituents of the glass arethen added. It is recommended that a littlered lead be added and nitrate of potash, andalso a very little oxide of tin. The proportion of gold to the other ingredients is usuallyabout one per mille, and a fine color may beobtained with even much less gold. The mixture is heated to a very high temperature, andis colorless at first. When reheated it beginsto color and the color gets darker the longerit is heated. This colored glass can be rendered colorless by a second reheating and slowcooling then the color can be again restoredby heating to a rather high temperature again.If, however, it is cooled suddenly the secondtime, it can not be made to become red again.This fact leads one to believe that no chemicalchange takes place, merely a molecular arrangement of the particles. The beautifulBohemian glass is made from a mixture ofruby and the purest crystal. A globe of hotcolorless glass is taken from the pot, and acake of ruby glass, made with schmelze, iswarmed and brought into contact with it. Theruby glass spreads quickly over the surface ofthe melted globe, and then the globe is blown,with a coating of the ruby glass on it. Schmelzeis made with 500 parts silica, 800 of minium,100 of nitre and 100 of potash. Then a verysmall portion of a solution of gold in aquaregia is mixed with 500 parts of schmelze, 43
Source:	http://indstate.contentdm.oclc.org/cdm/ref/collection/isuarchive/id/34532
Collection:	Indiana State University Archives

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