38 Gooch and Jones — Estimation of Boric Acid. 



our experience invariably differences of excess — presumably 

 because the loss due to volatilization of boric acid has been 

 overbalanced by the inaccuracy in washing. It is plain that 

 the process can give true indications only by the balancing of 

 considerable errors. 



If we take into consideration, therefore, the inevitable inac- 

 curacy and inconvenience of ThaddeefFs proposal, it cannot be 

 regarded as a desirable substitute for the process according to 

 which boric acid is absorbed and retained for weighing with 

 calcium oxide, especially since the difficulties in the way of 

 getting constant weights of that substance are by no means 

 insuperable. 



Thus the following table shows the series of weights taken 

 in several experiments in bringing calcium oxide to a constant 

 weight in a 50 cm3 platinum crucible ignited over a blast lamp, 

 as well as the weight taken after adding a known amount of 

 standard boric acid solution to the slaked oxide, evaporating, and 

 igniting. The results recorded are those of experiments made 

 on days not moist beyond the average and with the greatest 

 care to approach the limit of accuracy with which calcium 

 oxide and the boric acid held thereby can be weighed under 

 ordinarily favorable conditions. The first weight of calcium 

 oxide recorded under each experiment was taken after a strong 

 ignition over the blast lamp for about one-half hour. The suc- 

 ceeding weights were taken after similar ignition of five minutes. 

 In all cases the crucible was left to stand a definite period in a 

 sulphuric acid dessicator, and, after the approximate value had 

 once been obtained, the weights of the preceding weighing 

 were replaced on the balance before the crucible was taken 

 from the dessicator. The average of the weights bracketed is 

 the weight taken as constant for the calculations. 



(i) 



(2) 



(3) 



(*) 



CaO 



B 2 3 



CaO+B 2 



3 CaO + B 2 3 





taken. 



taken. 



taken. 



found. 



Error. 



grm. 



grm. 



grm. 



grm. 



grm. 



0-9505 







1-1590 ) - 





0-9493 | 0-9493 

 0-9493 \ 



0-2095 



1-1588 



1-1591 \ 1-1591 



+ 0-0003 











1-1319 







1-3499 





1-1317 ) 







1-3474 ) 





1-1313 I 1-1315 



0-2150 



1-3465 



1-3475 [ 1-3475 



+ 0*0010 



1-1315 ) 







1-3476 ) 





0-8028 







0-9205 





0-8025 | 0-8024 

 0-8024 \ 



0-1184 



0-9208 



0-9206 (09206 

 0-9206 j 



+ 0-0002 









2-6980 











2-6975 







2-9043 





2-6973 [2-6973 



0-2073 



2-9046 



2-9049 ) 2-9048 



+ 0-0002 



26973 f 







2-9044 \ 





