FORMATION OF FORMALDEHYDE IN CANE SUGAR. 175 



and Hehner, commercial sulphuric acid. 1 Reactions clear 

 and well defined were obtained by both Hehner's tests and 

 a faint reaction with Pilhastry's reagent, but no reaction 

 with the Gayon-Saglien-Mohler reagent. 



While carrying out these tests I found Hehner's milk- 

 sulphuric acid test most delicate; 1 part formalin in 4 

 millions gave a clear reaction in two minutes, and up to 1 

 in 10 million on standing a little longer, provided the milk 

 is added to the solution of formaldehyde immediately before 

 the addition of the sulphuric acid. The aqueous phenol 

 and sulphuric acid reacted up to 1 part in 4 millions. 

 Pilhastry's reagent seems to detect only 1 part in \ million 

 and the Gayon-Saglien-Mohler reagent about 1 part in \ 

 million. 



It has also been shown by Forster 2 that furfuraldehyde 

 is produced in small quantities by boiling sugar with water, 

 but in the experiments detailed above I find no furfural 

 reaction, only formaldehyde. In the case of furfural in 

 dilute aqueous solution with Hehner's test (milk sulphuric 

 acid), at the junction of the two liquids a faint pink zone 

 is formed, which darkens, forming a decided green colour 

 which deepens on standing. With Hehner's aqueous phenol 

 and sulphuric acid test applied to furfural, a purple black 

 band forms at junction of the liquids which deepens in 

 colour on standing and increases in size. These reactions 

 are quite dissimilar to the reactions of formaldehyde. 



1 Ibid., p. 121. 

 2 Forster, Berichte der deutschen Chemischen Gesellschaft, 15, 230 - 322. 



