738 PROCEEDINGS OF SECTION J. 
9.—COMPRESSED AIR AS A MECHANICAL MEDIUM 
IN THE EVAPORATION OF LIQUIDS. 
By A. O. Sacusz, C.E., M.E., M.S.E. Lond., F.R.G.S8., &e. 
[ Abstract. | 
In dealing with this subject, the author of the paper pointed out 
that there was no thoroughly satisfactory system of evaporating 
liquids at low temperatures yet.engineered. In the present method 
of boiling by open heat at a minimum temperature of 212 deg. F., 
he explained that many liquids of commercial manufacture were 
seriously damaged, principally by caramelisation, such as in the 
manufacture of sugar, the concentration of milk, meat extracts, 
and similar substances requiring condensation. After giving a 
careful consideration to the vacuum-pan systems, the author 
referred to extensive experiments conducted by him during the 
past 12 years, in which he made use of compressed air, injected 
into the body of a liquid (which was kept at a temperature of 
150 to 170 deg.), to produce a mechanical or artificial ebullition. 
The paper dwelt upon the success of these trials over the 
vacuum process, and called attention to the advantage of this 
system in regard to the liquid under treatment, being at all times 
exposed to view, and skimming could be freely practised ; whilst 
in existing vacuum “double” and “triple” effects the removal of 
impurities was a matter of impossibility, which was most injurious 
to the successful manufacture of many articles of food, and that 
in some districts large quantities of cold water for vacuum main- 
tenance were unobtainable. 
But whilst giving the compressed-air process much praise, he 
stated that the mechanisms now to be obtained for delivering 
dry air under pressure were unsatisfactory ; and as air-pumps 
were inefficacious for supplying large quantities of air, resort had 
to be made to rotary blowers, which latter exhibited many dis- 
advantages, principally on account of the great noise produced by 
them when working. Contrary to his expectations, he found that 
hot air when used produced less evaporative results than that 
taken in from the ordinary atmosphere. He advocated a careful 
research into the working of this peculiar system of evaporation, 
and demonstrated what a boon its successful application would 
prove to manufacturers dealing with liquid products requiring 
condensation, and especially so to proprietors of small installa- 
tions, where the heavy cost of purchase and working rendered the 
adoption of the vacuum process prohibitive. 
