PBODUCTION OF SULPHUEIC ACID. 3 



Theoretically this should prove the simplest, cheapest, and most 

 efficient method of making sulphuric acid, but in actual practice 

 there are several details encountered both in the construction and 

 running of a plant which unless given careful consideration will 

 seriously affect the yield of acid and the cost of production. 



Many different catalytic agents have been tried (notably platinum, 

 palladium, iridium, the oxides or sulphates of iron, copper, chromium 

 manganese, and silver, as well as the oxides of some of the rarer 

 elements) in effecting the oxidation of sulphur dioxide, but no matter 

 what catalyzer is used its efficiency is seriously impaired and often 

 destroyed unless very elaborate systems are employed ior purifying 

 the gases before admitting them into the oxidation chamber. For 

 instance, finely divided platinum (platinum black) has proved the 

 most efficient catalyzer so far discovered, but the catalytic power 

 of this body in bringing about the union of sulphur dioxide and air 

 is seriously affected by the smallest traces of arsenic in the gaseous 

 mixture. When pyrites are used as a source of sulphur dioxide, 

 the arsenic which this mineral nearly always contains, passes over 

 with the furnace gases and it is only by repeated washing and filter- 

 ing that the last traces of this element can be removed. 



Contrary to general opinion, therefore, a contact plant is both 

 elaborate and costly and strict supervision by a competent chemical 

 engineer is necessary to insure the best results. 



The contact process has distinct advantages over the lead-chamber 

 method where a pure concentrated acid is required, but in the manu- 

 facture of ordinary sulphuric acid (50° to 60° B.) for the fertilizer 

 industry or for other purposes where the purity of the product is 

 not essential, the latter method still holds first place (at least in this 

 country) for efficiency and low cost of production. 



THE LEAD-CHAMBER PROCESS. 



The lead-chamber process with its various modifications has been 

 fully treated by Lunge. 1 This author, as well as numerous other 

 investigators, notably Weber, Winkler, Rascheg, Meyer, Pratt, Gil- 

 christ, Falding, and Wedge, has described details of construction, 

 methods of accelerating the chamber reactions, and proposed and 

 discussed schemes for increasing the efficiency and lowering the cost 

 of acid systems. It is thought, however, that a brief general descrip- 

 tion of the chamber process will help toward a better understanding 

 of the modification of the process proposed in this paper. 



In this country nearly all of the sulphuric acid is made from 

 pyrites. The lump ore is imported chiefly from Spain, while the 

 "fines" are a domestic product mined in Virginia, Georgia, Ten- 

 nessee, and California. If the lump ore is used it is burned in brick 



1 Treatise on the Manufacture of Sulphuric Acid and Alkali, vol. 1. 



