132 CONSTRUCTION AND MANAGEMENT OF SMALL GASWORKS. 



at home. If a building or shed is not available, the plant 

 can be placed in a sheltered corner under a lean-to roof, care 

 being taken that the sulphate store is perfectly weather- 

 proof. 



If there is only one store tank, a fairly large settling 

 tank is required, to admit of the liquor being practically 

 free from tar. And it should be remembered that all wells 

 or tanks containing ammoniacal liquor must be perfectly 

 sound and tight. The smell of ammonia is objectionable 

 and injurious, and also a very appreciable money loss may 

 occur through leaky covers. The boiler having been 

 charged with the appropriate quantity of clear liquor, pre- 

 ferably of about 6 strength, the saturator is made up by 

 running in acid till a strength of 60 is shown on the hydro- 

 meter. If the saturator is already charged with mother 

 liquor remaining from a previous day's working, care should 

 be taken to see that the apertures in the coil are not 

 clogged with crystals. The hydrometer used for testing 

 liquor is known as a No. i, and has a scale from o to 24. 

 Another size, No. 3, scale 48 to 72", is used for the 

 saturator. The liquor is brought steadily up to the boil, 

 and as soon as ammonia begins to come over, any scum 

 that rises to the surface of the acid in the saturator is care- 

 fully skimmed off. Negligence in this respect, or waiting 

 till the liquid is thickly charged with salt, may result in a 

 dirty product. As soon as salt begins to collect, more 

 acid is run in, and care is taken not to let the strength of 

 the liquor fall below 56 or 54. The boiling is steadily 

 maintained, and the salt fished out as soon as possible. 

 The secret of making white salt is acid liquor and not too 

 long exposure in the saturator. If the boiling is slack, or the 

 supply of acid deficient, or the liquid not properly skimmed, 

 a bad yield of dirty salt may result. Sometimes lime or 



