202 PROCEEDINGS OF THE AMERICAN ACADEMY 



ZiNCic Oxide. 



Preliminary experiments with this substance gave results exactly 

 corresponding to those obtained from cupric oxide. If the substance 

 was prepared by ignition of the nitrate, very considerable amounts of 

 gas were found to be occluded ; while material of a similar grade of 

 purity in every other respect made by heating zincic carbonate ap- 

 peared to contain no trace of gas. 



The oxide used in the first three experiments was made by treating 

 so called pure zinc with nitric acid, evaporating to dryness, redissolv- 

 ing the zincic nitrate in water with the addition of a little nitric acid, 

 precipitating a small amount of iron with ammonia in slight excess, 

 evaporating the filtrate, and igniting the residue. This gave a faintly 

 yellow oxide. 



For the second series, a nearly neutral solution of fairly pure zincic 

 chloride was precipitated while boiling by a solution of sodic carbonate. 

 Part of the basic carbonate thus formed was ignited directly, the oxide 

 thus produced containing no occluded gas (Experiment 4). The 

 remainder was dissolved in nitric acid, evaporated to dryness, and 

 ignited to the full heat of the blast lamp in an open porcelain crucible. 

 Experiments 5, 6, and 7 are analyses of this yellowish sample. 



For the third series a solution of "chemically pure" zincic nitrate 

 was allowed to stand over an excess of zinc for some time. The fil- 

 tered solution was evaporated until a portion of the nitrate had been 

 converted into the basic salt. The whole was then poured into distilled 

 water, and a solution of normal nitrate was thus obtained after the 

 basic salt had been filtered off. This solution was treated a number 

 of times with zincic hydrate, — which had been precipitated by am- 

 monia and washed until free from the salts of this base, — and allowed 

 to stand. The filtered solution was evaporated to dryness and heated 

 in a porcelain crucible to about 240° C. over a ring burner. Part of 

 this was analyzed at once (Experiment 8), part heated by a Bunsen 

 burner (Experiments 9 and 10), and part ignited at a very high tem- 

 perature in a Hempel clay furnace with the blast lamp and bellows 

 (Experiments 11 and 12). Experiment 13 was made with a soft 

 white oxide prepared from the basic nitrate. 



Analyses 14 to 27 inclusive were made from oxide obtained as fol- 

 lows. Pure white zincic oxide of commerce was dissolved in nitric 

 acid, and carefully washed zincic carbonate was added to this solution 

 in slight excess. The whole was allowed to stand with occasional 

 shaking for some time, and finally filtered and evaporated rapidly by 



