84 CONSTRUCTION AND MANAGEMENT OF SMALL GASWORKS. 



dissolving pure crystallized acetate of lead in clean rain or 

 distilled water. The Gasworks Clauses Act 1871 specifies 

 60 grains of the crystals to one fluid ounce, equivalent to 

 about af ounces to the pint. If the solution is not quite 

 clear, a few drops of acetic acid may be added. The stock 

 bottle should not be kept in the purifier house, but a small 

 2-oz. wide- mouthed bottle should be used for the test, 

 and replenished as required, and both bottles should be 

 kept reasonably clean. For some reason or other, the lead 

 bottle will usually be found in the purifier house, and in a 

 disgracefully dirty state, caked with lime dust and black 

 stains from foul gas. Why this should be I do not know, 

 as the efficiency of the solution cannot be improved thereby. 

 A neater way of working is to use the ready prepared books 

 that can be obtained at about a shilling a dozen, sufficient 

 for a year's work, and to keep them in a box with a closely 

 fitting lid. A little bottle of pure water is all that is needed, 

 and a slip is torn out and moistened when required for use. 

 Daily testing with lead paper should never be neglected, 

 as the proportion of H 2 S remaining to be removed from 

 the gas is liable to fluctuate, and the efficiency of the material 

 used is not always the same. So it is not safe to depend 

 upon some primitive arrangement such as changing a 

 purifier once a week in the winter and once a fortnight in 

 the summer. If the boxes are exposed to the weather, a 

 sudden snap of cold will usually be found to prejudice the 

 working, as neither lime nor oxide is so active at. a tempera- 

 ture of 40 or less as it is at 50 to 6o e . If the purifiers are 

 enclosed in a building, it should be the rule to keep all 

 doors and windows shut up during cold weather, except, of 

 course, during the process of changing. The great point of 

 successful purification is to keep ahead of the requirement, 

 so as to avoid such a predicament as having a foul test at 



