498 Goocli and Kuzirian — Use of Sodium Paratungstate. 



In sodium paratungstate of composition corresponding 

 approximately to the formulae 5Na,,0.12W0 3 , or Na 10 "W ls O 41 , 

 we have material very easily prepared, stable in fusion, and 

 well suited for use as a flux in the rapid determination of the 

 loss of carbonates and nitrates on ignition. For the following 

 experiments the sodium paratungstate was prepared by dehy- 

 drating and fusing over the blast-lamp a known weight of 

 normal sodium tungstate, Na 2 W0 4 .2fl„0, adding an equal 

 weight of tungsten trioxide, WO, (previously ignited with care 

 to remove all ammonia and to insure complete oxidation), and 

 heating to clear fusion. The cooled mass, which is very easily 

 pulverized, was ground in a mortar and bottled. From this 

 material kept in a desiccator over sulphuric acid (though not 

 more than ordinarily hygroscopic), portions were weighed for 

 the analytical determinations. Approximately half the weight 

 of the paratungstate is tungsten trioxide (molecular weight 

 232) and this should be capable of expelling carbon dioxide 

 (molecular weight 14) to the amount of one-fifth its own 

 weight, and of nitrogen pentoxide (molecular weight 108*02) 

 to an amount one-half its own weight. The weights of 

 paratungstate used were, therefore, always in excess of ten 

 times the weight of carbon dioxide and four times the weight 

 of nitrogen pentoxide to be expelled. In the following deter- 

 minations it was the practice to weigh a platinum crucible, 

 introduce the dried carbonate and weigh again, add a suita- 

 ble amount of the prepared sodium paratungstate, stir carefully 

 Avith a platinum wire with care to avoid mechanical loss, and 

 weigh again. The crucible was heated over a bunsen burner, 

 first at very low heat and then to fusion of the mixture for five 

 minutes, cooled in a desiccator over sulphuric acid, weighed, 

 and re-ignited to test the constancy of weight. The constant 

 weight was usually got in the first ignition. In Table I are 

 given the results of the estimation of carbon dioxide in calcite. 







Table 



I. 









Analysis of 



Calcium Carbonate ( Calcite). 



CaC0 3 



NajoW^O,, 



Loss on 





Theory 





taken 



taken 



ignition 





for C0 2 



Error 



grm. 



grm. 



grm. 





grm. 



grm. 



0*5000 



2-5 



0-2195 





0-2198 



— 0-0003 



0-5000 



2*5 



0-2206 





0-2198 



— 0-0008 



0-5000 



2-5 



0-2200 





0-2198 



— 0-0002 



0-5000 



2-5 



0-2203 





0-2198 



— 0-0005 



0*5000 



2*5 



0-2200 





0-2198 



— 0-0002 



0-500O 



2-5 



0-2204 





0-2198 



— 0-0006 



0-5000 



2-5 



0-2190 





0-2198 



— 0-0002 



0-5000 



2 5 



0-2200 





0-2198 



— 0-0002 



