20 PROCEEDINGS OF THE AMERICAN ACADEMY 



It follows from what has been said on this subject, that care must be 

 taken not to continue longer than is absolutely necessary the treat- 

 ment with alcohol during the prepai'atiou of tlie sodic zincate. Al- 

 though the substance is decomp»sed by both alcohol and water, it 

 seems to exist during the process of manufacture dissolved in a mix- 

 ture of these solvents in presence of an excess of sodic hydrate, an 

 observation which is confirmed by that of Prescott (see page 15). It 

 is insoluble in ether, and absorbs carbonic dioxide rapidly from the 

 air. At 100° it loses only 12 molecules of its water of crystallization, 

 as is shown by the following analysis. 



0.4720 grm. of the substance analyzed under I., when heated to 100° 

 in a stream of pure dry air, lost 0.1510 grm. of water. 



Water 



Analyses and Properties of the Infusible Sodic Ziiicate, 

 (ZnO-^NaH), . 7 H.O. 



This substance, which crystallizes from the alcoholic washings 

 obtained in the preparation of the fusible compound just described, is 

 formed in comparatively small quantities. As nearly as we could 

 estimate, only a few per cent of the total product consisted of it. A«, 

 like the fusible compound, it is decomposed by both water and alcohol, 

 no attempt was made to purify it further, but it was analyzed after 

 drying at ordinary temperatures by the method already described (see 

 page 17). 



I. 0.7470 grm. of the substance gave 0.3424 grm. of zincic oxide 



and 0.2913 grm. of sodic sulphate; 0.4762 grm. of substance 

 from the same preparation lost at 220° 0.1637 grm, of water. 



II. 0.6044 grm. of the substance lost at 300° 0.2066 grm. of water, 



and gave 0.2700 grm. of zincic oxide and 0.2355 grm. of 

 sodic sulphate. 



Calculated for Found. 



(ZnO^NaHj-JHoO. I. H. 



Zinc 35.32 36.78 35.86 



Sodium 12.50 12.62 12.62 



Water 34.24 34.37 34.19 



The considerable difference between the percentages of zinc is not 

 greater than was to be expected, when the impossibility of purifying 



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