The DETERMINATION of ALKALI IN ARSENICAL 



DIP-FLUID. 



By L. Cohen, Chemical Laboratory, Department of 



Agriculture. 



[Communicated by F. B. Guthrie, f.i.c, f.c.s.] 



[Read before the Royal Society of N. S. Wales, June 1, 1910.} 



The determination of alkali in dip-fluid by direct titration 

 against standard acid is complicated by the presence of 

 tar and finely divided foreign matter from the hides of the 

 cattle, which it is impossible to separate by filtration, and 

 the black colour of which precludes the use of an indicator, 

 except in the form of test-paper. 



If litmus paper is used, the carbon dioxide, and perhaps 

 also the arsenious acid, indicate an acid reaction before all 

 the sodium carbonate is neutralised, it consequently gives 

 results a good deal too low. Besides this, the process of 

 taking out a drop of the solution on a glass rod from time 

 to time during titration, placing it on the paper, allowing 

 it to remain a few seconds and then washing off, is a tedious 

 one, and leaves much to be desired even if the sample is 

 first rendered acid, boiled to expel C0 2 , and then titrated 



The composition of the cattle-dip made according to the 

 Departmental formula is : — 



Arsenic (As 2 3 ) 8 lbs 2 grams. 



Washing soda 10 lbs. = Na 2 0O, 3*706 lbs. '92 grams. 



Tar \ gall. = 5'25 lbs 1*31 grams. 



Soap 1 lb '25 grams. 



Water 400 gallons 1000 cc. 



