204 PROCEEDINGS OP THE AMERICAN ACADEMY 



Upon dilution the basic nitrate, which contained most of the impurities 

 not deposited upon the zinc, was precipitated and removed by filtra- 

 tion. Tbe solution was then evaporated to dryness and the residue 

 ignited in porcelain. (See Experiments 28 and 29.) Another sample 

 of zinc was dissolved in a similar way in platinum, and the resulting 

 solution of the pure nitrate was divided into several portions. One 

 portion was evaporated in glass and ignited in porcelain, the residue 

 containing somewhat more gas than that which had been treated 

 wholly in porcelain. (See Experiments 30, 31, 32, and 33.) An- 

 other part was evaporated and ignited in platinum (Experiment 34). 

 This sample was undoubtedly reduced in part by the diffusion of gases 

 from the flame.* Still another portion was ignited for a short time 

 only in platinum, the ignition being completed in porcelain (Experi- 

 ment 35). A fourth portion was ignited for a short time in an open 

 platinum dish with free access of air (Exjieriment 3G). Finally, the 

 remainder of the solution of pure zincic nitrate was evaporated and 

 ignited in a platinum vessel enclosed within one of porcelain. This 

 specimen was not exposed to the action of reducing gases, and upon 

 solution it evolved almost exactly the same amount of gas as the 

 specimen which had been prepared in glass and ignited in porcelain. 

 (See Experiments 37 and 38.) 



Experiment 39, using zincic oxide prepared from the carbonate, 

 was made to test again the accuracy of the method. 



The weight of zincic oxide taken for each individual experiment is 

 tabulated in the second column of the following table, and the third 

 column indicates approximately the conditions used for the ignition of 

 the different portions. The volume of gas given off on the subsequent 

 solution of the zincic oxide in sulphuric acid is recorded in the fourth 

 column, while the fifth contains the same data reduced to the stan- 

 dard of ten grams of zincic oxide. The sixth column contains a record 

 of the analyses of the gases, and the seventh supplies information upon 

 a few minor points connected with individual results. 



* Erdmann, Pogg. Aunal., LXII. 611. Morse and Burton, Am. Chem. Journ., 

 X. 311-321. 



