568 Transactions. — Physics. 



Art. LX. — The Distillation of the Fatty Acids for the 

 Manufacture of Candles. 



By P. W. Eobebtson, B.A., Senior Scholar. 



[Read before the Wellington Philosophical Society, 6th July, 1904.] 



Many processes have been suggested for the preparation of 

 the fatty acids from tallow. Of these, the only one practised 

 in New Zealand is that in which the tallow is hydrolised by 

 means of a small quantity of sulphuric acid. The acids thus 

 obtained are washed free from the sulphuric acid and gly- 

 cerine, and then distilled in superheated steam. 



The products of the distillation have been investigated by 

 Cahours, who paid attention to the volatile portions of the 

 distillate, consisting essentially of a number of the lower fatty 

 acids. The object of the present investigation was to examine 

 the course of the distillation from a physico-chemical stand- 

 point, and no attention was paid to the volatile by-products. 



Only in one factory in New Zealand is the distillation 

 conducted in a copper retort, and in this case, as soon as the 

 charge begins to become yellow it is blown into an iron 

 retort, in which, after four or five charges have been collected, 

 the distillation is concluded. In the factory :;c where the ex- 

 periments were conducted the whole charge is distilled from 

 an iron retort ; the last portions, being too soft and dis- 

 coloured for candle-making, are returned to the retort and 

 distilled with the next charge. The fatty acids condense in 

 a number of coils, the first three of which collect practically 

 the whole of the distillate. 



The freezing-point is a most important property to the 

 candle- manufacturer, as the magnitude of this constant gives 

 a direct measure of the hardness of the material, and hence 

 its suitability for candle-making. Consequently, these data 

 were studied in great detail. At the outset it was found 

 that it would be much better to ascertain the temperature of 

 freezing rather than the melting point, for in the latter 

 case definite results could not always be obtained : hence 

 in the whole operation the freezing-points were determined. 

 To make the observation the bulb of the thermometer was 

 placed in the melted sample, and then held in a small beaker 

 to avoid the influence of air-currents. The mean of two or 

 three determinations was taken as the final result. 



* I beg to take this opportunity of thanking the Directors of the New 

 Zealand Candle Company for the kindness with which I was treated when 

 performing the experiments at their works. 



