197 



JOSEPH L. McCarthy 



"A. Estimations in 16 separate laboratories 

 of spent sulfite liquor concentrations in five sample 

 waters using substantially the procedure of the standardized 

 method yielded results showing standard deviations in net 

 absorbances of about plus or minu-s 0.00? to 0.014 equivaltnt 

 to about plus or minus 3 to 6 parts per uillion of spent 

 sulfite liquor containing 10 percent total solids." 



Our fifth and last conclusion in part was 

 as follows: 



"Although this standardized Pearl-Benson 

 or nitroso method for estimation of spent sulfite liquor 

 concentration gives satisfactorily reproducible results 

 and is relatively simple to carry out, the nitroso pro- 

 cedure may lead to erroneously high results when inter- 

 fering substances are present." 



To illustrate this phenomena, the following 

 paragraph is quoted from Page 34A of our published paper: 



"Waters I, IV, VIII, and X were salt, 

 fresh, fresh, and salt water samples, respectively, from 

 the Pacific Ocean, Lake Washington, Quilceda Crc '-, and 

 Deception Pass, respectively, into which no spent sulfite 

 liquor is discharged and no spent liquor was added to the 

 samples. However, about 2,8, 1 and 3 parts per million 



of apparent spent sulfite liquor concentrations. 



