409 



4- TREATMENT OF BY-PRODUCTS OF THE MANUFACTURE OF COAL-GAS. 



The great toxicity of nearly all the representatives of the chief 

 groups of compounds occurring as by-products of the manufacture 

 of' coal-gas render it inadvisable to permit the pollution of streams 

 with any of these compounds. Attention is especially directed to the 

 fact that the compounds commonly reckoned as insoluble in water by 

 industrial chemists are among the most deadly. Further it must be 

 noted that the volatile and gaseous products such as ethvlene. carbon 

 monoxide, benzene, xylene, etc., which doubtless go into solution in 

 the water which is used for washing gases during manufacture, and 

 which are least likely to be suspected of being detrimental, are among 

 the most poisonous compounds and probably the most universally 

 thrown into streams. Marsh ('07) has shown further that effluent 

 from an ammonia sludge-bed, lime and iron oxide from purilicrs and 

 residuals from water-gas are very toxic. 



In general the experiments leave no doubt but that earnest effort 

 should be made to prevent the introduction of anything whatsoever 

 in the way of coal-gas products into stream and bodies of water. No 

 matter what method of treating the wastes may be devised the general 

 toxicity of the entire series of compounds makes it certain that much 

 damage will result from pollution with the residues of any form of 

 treatment. In general however the damage to fishes will be greatest 

 in connection with the smaller plants which ordinarily save only the 

 heavy tar or at most tar and ammonia. If the government cannot 

 compel gas manufacturers to make their valuable but poisonous by- 

 products into something useful, it can at least make such an industry 

 advisable by preventing the addition of these waste materials to 

 streams, and if necessary conduct investigations into methods for the 

 profitable disposal of the entire series of these by-products. 



VIII. Summary. 



1. Illuminating gas, gas-Hquor, and thirty-one out of thirty-four 

 representatives of the chief groups of compounds found in gas and 

 gas-liquor are very toxic to fishes. From one to fifteen hundred parts 

 per million are fatal to an orange-spotted sunfish in one hour. 



(P-39I) . , t 



2. As a rule the smaller fishes are more readily affected than the 

 larger, down to the smallest fry studied; the minimum amount of the 

 various substances required to kill fishes must be established by using 

 the most sensitive stages, which are probablv the smallest fry. 

 (P. 407.) 



