﻿Manchester Memoirs \ Vol. xlix. (1905), No. 10. 



XVI. Two New Aldehyde Reactions. 



By W. B. Ramsden, B.Sc, M.B., Ch.B. 



(Communicated by Mr. D. L. Chapman^ M.A.). 



Received February 21st. Read March yth, /goj. 



In the course of some investigations, on which I am 

 now engaged at the suggestion of Professor Delepine, 

 concerning the action and behaviour of formaldehyde as 

 a preservative in food, it became necessary that some 

 delicate and simple method of detecting the formaldehyde 

 should be used, which is capable at the same time of 

 being employed as a quick method of estimation. After 

 a survey of the various ways of determining formaldehyde 

 I am now using the cyanide method of Romjin (1) for the 

 stronger solutions. For the weaker solutions I employ a 

 modification of the method given by MM. Seyewetz and 

 Gibello in the Bulletin de la Societe Chemique de Paris 

 (June, 1904). These authors estimate the formaldehyde 

 by means of sodium sulphite. Starting with a 20 per 

 cent, solution of sodium sulphite they first neutralise 

 20 ccs. of it with standard H 2 S0 4 using a 0'2 per cent, 

 solution of phenolphthalein as an indicator. The quantity 

 of H0SO4 required for this purpose is determined once for 

 all. In another portion of the sulphite a known volume of 

 the formaldelhyde solution is added and a second titration 

 with H n S0 4 carried out. The difference in the two 

 titrations gives a measure of the formaldehyde in the 

 solution according to their equation 



2 Na 2 S0 3 + 2HCHO + H a S0 4 =2(NaHSO,HCHO) + Na 2 S0 4 . 

 In order to detect formaldehyde in solutions too dilute 

 to be estimated by this method, I have modified the test 



June 3rd, 1905. 



