Seven colonmetoc methods were conducted to delect formalin in either in
water solutions, or in milk containing differe.,! concentration of formalin (1-1000 ppm).
The methcds used were : Hehner's test (1) : Leech's lest (2) ; Shrewsbury and
Knapp's test (3) : Nash's reagent (4): ChromotroplC acid method (5) , Schryver's test
(6j and phenylhydrazin potasslurn (errocyanid test (7). It was noticed that methods (4)
and (5) were more sensitive than others (or detecting formalin In water solutions.
whereas the most ssnsnive methods to detect formalin in milk samples were (2), (4i
and (5). On the other hand. with water-base solution. methods (1), (2) and (3) failed 10
detect either low Of high formalin concentrations, while methods (6) and (7) failed only
tc detect the lower concentrations. The same trend was obtained with milk samples
except method (2) which was sensitive for all concentrations. Methods (4) and (5) were selected to detecte the presence of formalin in the
whey of acid coagulation cow's milk (with sulphuri¢ or ac=tic acid), and in the distilate
obtained by indirect distilation of milk samples. The results obtained by using method
(4) were always less than the actual polluted concentralions and represent - 58-62%
in the case of acid whey and 37-52% in the indirect dislilation method. Examination 01
the presence of formalin in acid whey by using method (5) 10 detect it, however, more
accurate results were obtained by using indirecl distilalion method compared with
method (4) (5:'-70% vs, 37-52%, respectively)