Page:The American Cyclopædia (1879) Volume XV.djvu/261

 SPECTRUM 249 and containing a solution of cupric sulphate in ammonia. The general phenomena of fluores- cence are described under FLUORESCENCE ; we here add several discoveries made since the writing of that article by Prof. Morton of Ho- boken. In a portion of his researches Prof. Morton had the cooperation of Dr. H. C. Bolton of New York, who undertook the chemical work in the investi- gations. Their attention was particularly directed to the fluorescent properties of the uranium salts. The total num- ber of distinct salts produced and examined so far by these investigators is 75, not in- cluding numerous specimens treated in various ways to es- tablish the existence and con- ditions of their several hy- drates. This multiplication of facts has given great value to this research as compared with previous work in the same direction. Thus, where Becquerel has examined one double acetate, these investi- gators have examined 16; in place of his three double sulphates, they have 16; in place of one fluoride, six; and so on. The methods pursued in the examination of these uranium salts were the same as those of Stokes and Becquerel. The discoveries made by Morton were mainly due to the wider range of substances examined, which made it possi- ble to form inductions and generalizations, and to the scrupulous attention paid to the purity of these substances. "We note only the most important results, and refer the reader to the following original papers for additional infor- mation: "American Chemist," vols. iii. and iv. ; "Chemical News," vol. xxviii. 1. By a comparison of the spectra of 17 acetates and double acetates of uranium in the solid state and in aqueous solutions, the remarkable fact was demonstrated that in the case of these bodies no double salt could exist in solution in water. By further experiments of the same kind this law was ex- tended to all the known salts of uranium. 2. It was proved that by the study of the fluorescent spectra the existence of a new and be- fore unknown salt could be recognized. Thus, on heating the ammonio- uranic sulphate to 100 C. for a short time, it was noticed that its fluorescent spectrum assumed a duplicate character (see spectrum 2 of fig. 10), a new set of bands being 'add- ed to those of the normal salt (see spectrum 1 of fig. 10). By continuing the heating until the salt ceased to lose weight, a substance was obtained giving spectrum No. 3 of fig. 10. These results naturally suggested that the two spectra 1 and 3 belonged to the hydrated and anhydrous salts, and that spectrum 2 indicated FIG. 10. a mixture of the two. On heating the dried salt to low redness for a short time, another double spectrum, No. 4, was developed, which by a continuance of the same treatment was reduced to a new simple one, No. 5. Analysis of the product so obtained showed that it was an ammonio-diuranic sulphate, a salt before unknown and not likely to have been discov- ered by any other means, as contact with water at once reduces it to a mixture of the normal salt and uranic sulphate. 3. It was discovered that certain uranic salts were capable of com- bining with definite proportions of water to form certain hydrates not heretofore recog- FlG. 11. nized, and that each of these hydrates yielded a perfectly distinct and characteristic spectrum. Thus, the double sulphate of sodium and ura- nium seems to form no less than five hydrates with from one to five atoms of water respec- tively. These salts have not all been isolated,