82 CONSTRUCTION AND MANAGEMENT OF SMALL GASWORKS. 



place for a gauge is the immediate outlet of the hydraulic, 

 particularly when there is no exhauster. Cocks should be 

 fixed at various points, such as hydraulic, inlet and outlet 

 of condenser, ditto of washer and of each purifier, and the 

 gauge should be fitted in a metal case, so that it can be 

 conveniently shifted from point to point. 



While an elaborate regulation of the hydraulic seal is 

 not to be expected, there is no difficulty in adjusting it to 

 less than one inch. 



Self-sealing retort lids are rather too great a refinement 

 for the average small works, but there is no occasion to use 

 all clean lime for luting. It can be mixed with a good 

 proportion of clay, loam, or spent lime, and sometimes 

 other refuse material is obtainable. 



One often meets with the expression, " a good carbonizer," 

 used by people who do not understand the meaning of the 

 term. It is strict and careful attention to details such as 

 the above that constitute good carbonizing, rather than any 

 special talent or genius. 



For testing the ammoniacal liquor, a No. i Twaddel 

 hydrometer is used, having a scale extending from o to 

 24. A degree is equivalent to 2 oz. strength. A 

 5 liquor is, therefore, 10 oz., and a 6, 12 oz. Care 

 must be taken to see that the hydrometer is fairly 

 accurate, as sometimes the instrument is found to be as 

 much as i J or 2 out ; which is a serious matter if the 

 liquor is to be got up to a particular strength, or when it is 

 sold at so much per degree or per ounce. If there is any 

 appreciable quantity of light oil or tar in the liquor, the 

 result will not be reliable ; and the same applies to tests 

 taken on a flowing stream, such as at the seal box at outlet 

 of scrubber. I have found it a good plan, if there is any 

 doubt about the accuracy of the hydrometer, to get the 



