48 THE QUANTITA\ 7 E SYNTHESIS OF ARGENTIC NITRATE, ETC. 



portion of each distillate. None of the samples left a trace of nonvolatile 

 residue on evaporation. No difference could be detected in the results 

 because of the difference of source of the acid, nor was the constancy 

 destroyed when a single distillation only was made. (Experiment 11.) 

 Hence little anxiety was felt concerning the purity of this material. 



Silver. - - The researches of Richards and Wells have shown how to 

 prepare silver of unquestioned purity. Preliminary determinations 1, 2, 

 3, 4, 5, 7, and 8 were made on a sample (A) left over from the above- 

 mentioned research, crystallized fifteen times with nitric acid, precipitated 

 with formate, and fused on purest charcoal, but not electrolyzed or fused 

 in hydrogen. No. 9 was made with a sample prepared by Professor 

 Baxter for his final work on bromine. It had been through the chloride 

 and formate treatment, electrolyzed, fused in hydrogen, cut with a saw, 

 etched with nitric acid, boiled with water, dried at dull redness in vacuo, 

 and given us ready to weigh. We are much indebted to him for furnishing 

 this check on our silver. The final determinations were made with silver 

 derived from several preparations. The first of these (C) was recrystal- 

 lized sixteen times as nitrate from water and redistilled nitric acid, and 

 then precipitated twice in succession with formate. A part of the final 

 formate product was fused on the best lime in carefully purified hydrogen 

 made from aluminum and sodic hydroxide. Sample D had been precipi- 

 tated as chloride, reduced with best alkaline sugar, washed free from 

 chloride, dissolved in nitric acid, filtered and crystallized as nitrate in 

 platinum six times from nitric acid distilled in a platinum condenser. 

 Centrifugal treatment eliminated the mother liquor. The last crop of 

 crystals was precipitated with formate in a silver dish, washed free from 

 ammonia, and fused in a cup of pure lime. Sample F was obtained by 

 the electrolysis of a button of very pure silver from Colorado, which had 

 been fifteen times recrystallized as nitrate, precipitated with formate, and 

 fused on lime. Samples C, D, and F were all cleaned by etching and then 

 purified by electrolysis through a nitrate solution made from some of the 

 same silver and the purest nitric acid. They were then fused separately, 

 on a well-seasoned lime boat, in a new porcelain tube, in an atmosphere 

 of pure electrolytic hydrogen. The Hempel stoppers fitted so well that 

 the pressure could easily be reduced to a fraction of a millimeter by a 

 Geryk oil-pump when desired. The heating was accomplished by a large 

 Heraeus electric furnace which fused the silver without overheating any 

 part of the tube. In all cases the initial fusion was completed in hydrogen 

 at atmospheric pressure, but in half the fusions the tube was evacuated 

 before the temperature was lowered. No spurting or boiling could be 

 observed through the glass window when the pressure was reduced, and 



