246 Scientific Proceedings, Royal Dublin Society. 



The variation in the weight of water per e.c. of distillate appears to 

 account for the variation in A with concentration within the limits of 



A 

 experimental error; — gives the limiting value of A for verv dilute 



solutions. 



Preimration of n-Butyl-n-butyrate. 



In the estimation of «-butyl alcohol with potassium dichromate and 

 sulphuric acid, it was previously noted that some ester was formed when the 

 oxidation was carried out under certain conditions. The conditions which 

 facilitate the formation of this ester were studied as a separate problem. 



Ti-Butyl alcohol (148 grams) was added to a solution of potassium 

 dichromate (200 grams) in sulphuric acid (276 grams in 750 grams 

 of water). Precautions were taken during the addition of the alcohol to 

 prevent the temperature from rising above 30-40°, otherwise the reaction 

 would tend to become vigorous, especially when the alcohol is added too 

 quickly. When the addition was complete, the reaction-mixture was heated 

 for 2-6 hours on a water bath. If the oxidation proceeded satisfactorily, a 

 light-coloured oil was obtained, with a quantity of dark-green lower aqueous 

 layer. 



The oil consisted chiefly of ?i-butyl-w-butyrate, together with a small 

 amount of unchanged alcohol and products boiling above 190°, and»usually a 

 trace of butylaldehyde. In the best experiments a 75 per cent, yield of 

 7i-butyl-?i.-butyrate was obtained on the original weight of alcohol taken. 

 During some of the experiments, notably those in which the duration of 

 heating was short, the ester layer was contaminated with a green substance. 

 This substance contained chromium, and appeared to be slightly volatile in 

 the vapour of 7i.-butyl-?i-butyrate, for, on distillation of the crude ester, the 

 main fraction was coloured green. It was obtained in a crude state by 

 removing the volatile portions from the residue remaining in the flask 

 after distillation. It was a dark-green amorphous mass, readily soluble in 

 acetone. 



As a product of the reaction there was always present a small amount of 

 a substance of higher boiling point than 7i-butyl-w-butyrate. The yield of 

 the substance was found to be increased by allowing the oxidation to be 

 completed at laboratory temperature. 



The formation of the n-butyl-w-butyrate may be explained by assuming 

 the intermediate formation of butyric acid which is esterfied by the alcohol. 

 Butyric acid, in fact, has been detected from the aqueous layer, and is usually 

 a product of the reaction. 



