676 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1913. 



means, in round numbers, a mean linear velocit}^ in the flue shown 

 of 10 to 20 feet per second. 



Before attempting to design the full-sized equipment for treating 

 these gases a small precipitation chamber capable of treating about 

 1 per cent of the total gases was erected and an extended set of ex- 

 periments made with it. Figure 22 shows this small unit with its 

 exhaust fan and stack. In the original tests it was located nearer 

 the base of the main stock, the figure showing it as later modified for 

 other experiments and tests. 



Figures 23 and 24 indicate the degree of success attained with this 

 small unit in its original position, having been taken a few minutes 

 apart with the electric current respectively off and on, the same gas 

 ^'olume issuing in both instances from the stack, which is 2 feet in 

 diameter. 



With this miniature unit as a guide, the equipment of the whole 

 plant with similar apparatus was undertaken in March, 1910. This 

 was completed and first put into operation the end of the following 

 September, and with the exception of a couple of weeks in December, 

 remained in continuous operation until July 24, 1911, when the whole 

 plant shut down until such time as a practical method could be found 

 for removing from the gases not onlj^ the suspended solids, but the 

 sulphur dioxide gas as well. Experiments to this end with the Hall 

 process already referred to, upon at least a semicoimnercial scale, 

 have since been pursued by the Balaklala Co. at the smelter; but no 

 decision seems yet to have been reached regarding their commercial 

 practicability on the full-sized operating scale of the smelter. These 

 experiments on sulphur dioxide have, however, nothing fimdamen- 

 tally to do with the electrical precipitation, and returning to this it 

 may be said that the nine months of operation which the plant had 

 amply demonstrated the entire practicability of extension of the 

 process to operation of this and even larger scale. 



As was naturally to be expected man}'- difiiculties were encountered, 

 some of which were quickly overcome, while others gave way more 

 gradually before the systematic study of operating conditions. 



Figure 25 is a plan of the nine electrical precipitation units or 

 chambers in their relation to the flue system and stack. It should 

 here be noted that the two large fans indicated in the drawing were 

 not required for the operation of the precipitating system nor to over- 

 come any resistance due to its introduction, as this latter was veiy 

 slight indeed. The fans were made necessary by that section of the 

 court's decree requiring dilution of the sulphur dioxide to three- 

 quarters of one per cent or less. Wlien the furnaces were running on a 

 high sulphur charge this feature of the decree necessitated a consider- 

 able dilution of the gases with fresh air and corresponding diminu- 

 tion of stack draft. At such times the fans were operated, but during 



