PAPERS ON WATER SUPPLY 



75 



THE ARSENIC CONTENT OF FILTER ALUM USED 

 BY ILLINOIS WATER PURIFICATION PLANTS 



A. N. Bennett, Chicago, III. 



Introduction 



Specifications requiring arsenic free alum for water treat- 

 ment by several European 1 purification plants suggested to 

 us that it would be advisable to make determinations of the 

 arsenic content of the filter alum used in the State of Illinois. 



It is well known that products which are manufactured 

 with the aid of commercial sulfuric acid quite generally con- 

 tain more or less arsenic, depending upon the purity of the acid 

 used. The poisonous character of arsenic compounds, even 

 when present in small amounts, makes it of general interest 

 and importance to have definite knowledge of the presence or 

 absence of arsenic in any substance which enters directly or 

 indirectly into foods or drinks. Sulfuric acid is used in the 

 manufacture of filter alum and it is thus quite essential, par- 

 ticularly to those who are in public health work, to know 

 whether arsenic in any considerable amounts is being added 

 to drinking water in the process of purification with alum. 



We have not been able to learn that anything has been done 

 in this country to regulate the amount of arsenic in filter alum. 

 The purification plants (at least in this State) have made no 

 effort to obtain an arsenic free article. The manufacturers of 

 alum keep more or less accurate records of the arsenic content 

 of their product, but (we have found no published records. We 

 have found only one producer who advertises "arsenic free 

 alum." Neither the government nor any of the States have 

 promulgated legislation regulating this product, although there 

 is a regulation concerning arsenic in other substances entering 

 into foods. The government has set a limit for arsenic in 

 coal tar dyes and in baking powder of one part in 700,000. 

 This very low limit, particularly when it is considered that 

 only relatively small amounts of these substances are used in 

 food preparation, shows that considerable importance is at- 

 tached to the presence of arsenic and its compounds. 



Samples: In order that our results might be of greatest 

 value by showing the condition of the alums as they are actual- 

 ly used, we obtained as many samples as possible directly from 

 the various purification plants in the state. Twenty-six plants 

 use alum in treating the water. The purpose of our investiga- 



1. Jour. f. Gasbel: 1913 (Sept.) 



