232 



CHEMICAL MANUEES. 



density of the ammoniacal water ought to be taken, and it must be 

 seen that the escaping gas contains no trace of ammonia. 



Chevalet constructed a scrubber of wrought-iron or of cast-iron,, 

 containing cast-iron vessels 8 inches apart and pierced with a great 

 number of holes, carrying a chimney a little less in height than the- 



Fig. 39. — Standard Washer furnished with its different Discs. — The upper tigure 

 shows the outside appearance of the face of the washer ; in the lower figure 

 the washer is seen from above ; the top side has been partly removed to show 

 the interior arrangement. The discs of Fig. 38 are sho^Mi mounted side by 

 side on the same shaft ; their lower part dips in the water when the shaft 

 turns ; the moistened discs come in contact with the gas which passes to the 

 upper part. This latter is dissolved. A peculiar system of partitions forces 

 the gas to enter into intimate contact with the rods of the discs and to 

 dissolve almost completely. 



edge of the vessels. Each vessel is fixed in a ring without bottom 

 of the distilling column. Between each vessel wooden shavings 

 or coke is packed. 



Distilling Plant. — All methods used to manufacture sulphate of 

 ammonia consist essentially in disengaging ammonia from its salts^ 

 in submitting it to distillation, in conducting the ammoniacal 



