PURIFIERS. 115 



prevent even the smallest waste. This care, to some, may appear frivolous 

 and unimportant ; but if ceconomy is to exist in a gas establishment, there is 

 no better method of preserving it than by order, and attention to detail. 

 Almost all gas-works are more or less slovenly, and it will be found on exa- 

 mination that want of system is the cause ; some degree of dirt, if I may use 

 the expression, is quite unavoidable, but order will always prevent that dirt 

 becoming a nuisance. 



The arrangement of valves connected with this part of the apparatus is of 

 consequence. I decidedly prefer one hydraulic valve to four or more slide- 

 valves, for the reason that if the man whose duty it is to attend to them were 

 to shut those leading to the spent purifiers before he opened the others, the 

 consequences would be serious ; the sudden check given to the exit of the gas 

 from the retorts would drive the tar from the hydraulic main up the dip-pipes 

 into the open retorts, if there happened to be any, and most probably do much 

 injury. I have myself witnessed several accidents from this cause. With the 

 one hydraulic valve this cannot occur, for it is impossible to close one par- 

 tition without opening another. They are much cheaper, less liable, or not 

 liable at all to be out of order, and altogether more advantageous. As a sub- 

 stitute for the wash -vessel already described for cleansing the impure gas from 

 essential oils and ammonia, the " breeze condenser" is preferred by some; 

 the action of which is quite mechanical, but answers the purpose of removing 

 a considerable portion of the tar and fatty oils. Its construction is similar to 

 a dry-lime purifier, layers of " breeze," or coke-dust and cinders being laid 

 upon the screens instead of hydrate of lime ; the layers may nearly fill up 

 the space between the screens, and have a surface of one square foot for every 

 5000 cubic feet of gas which passes through them. The reason of the pre- 

 ference given to these is, that the olefiant gas and heavy carburets are not 

 absorbed, which will be the case in some considerable degree when it passes 

 through water, that fluid being capable of taking up one-eighth of its volume of 

 olefiant gas. It is a matter of practical opinion whether the essential oil still 

 contained in the gas, after having passed the " breeze condenser," is more 

 injurious than the presence of olefiant gas is beneficial. It has been proposed 

 to use a solution of the muriate of potash in the wash-vessel to absorb the 

 carbonic oxide, which pure water will not effect ; but the portion of this gas 

 generally contained in that from coal is not worth the expense that would be 

 attendant upon the use of muriate of potash. The arrangement of the vessels 



Q2 



