PRESERVATION AND STORAGE. 269 



This defect having been recognised, bins hned with sheet 

 metal were introduced as storage receptacles, the lids being 

 soldered down after filling. Simultaneously, cylindrical 

 drums of galvanised iron came into use for the conveyance 

 and storage of hops. Latterly, to protect the hops from 

 atmospheric action the custom has arisen of pumping the 

 air out of the filled cylinders after they have been closed by 

 an air-tight lid ; and occasionally carbonic acid gas or sul- 

 phurous acid gas is introduced to fill the resulting vacuum. 

 Far-reaching importance — whether rightly or no — has now 

 been attained by the process of sulphuring the hops in the 

 kiln. Originally practised in England and America, sul- 

 phuring was introduced on the Continent in the " fifties," and 

 at the present time the great majority of commercial hops 

 are treated by this process. It is, bowever, seldom performed 

 by the (Continental) grower himself, though the burning of 

 sulphur in the kilns greatly accelerates drying, but is mostly 

 left to the merchant. The purchased hops are spread out 

 about eight inches deep in a kiln arranged like a malt< 

 kiln, and are re-dried and sulphured, the sulphur being 

 burned in open pans underneath the kiln floor, or else in 

 special sulphur stoves. The sulphurous acid gas liberated 

 by this operation traverses the layer of hops, and, in addition 

 to destroying large numbers of micro-organisms, also im- 

 proves the colour. The excess of gas is generally carried 

 o£f through the ventilating cowl at the top of the kiln ; but, 

 where the treatment is practised in towns, means must be 

 devised for preventing the escape of the gas into the open 

 air — generally by passing the outgoing air through an inter- 

 mediate chamber containing caustic soda or some other 

 substance capable of combining with the gas. The amount 

 of sulphur required is usually taken as from 1 to 2 per cent, 

 of the weight of the hops in the kihi ; and the combustion 

 is so regulated that the hops are exposed to the action of the 



