TRANSACTIONS OF SECTION B. 301 



G. Lead Fume, with a Description of a Neiv Process of Fume Condensing. 



By A. French. 



1. The great loss of lead, and sometimes silver, by volatilisation induced Messrs. 

 Wilson and myself to investigate the physical nature and deportment of metallic 

 fumes as they exist in the furnace and in the flues. 



2. The following is a classification of the various methods of condensing: : — ■ 



(a) Deposition by its own gravity in long flues, with or without the addition of 

 settling chambers. 



(b) Filtering through porous materials, such as coke, brushwood, or coarsely' 

 woven fabrics. 



(c) The use of water, either in the form of steam or in spray projected across 

 the flue current. 



(d) Processes based on the inverse of the preceding principle, viz., passing the 

 lead smoke under and through water in a more or less comminuted conditiou. 



3. We made experiments to prove the efficacy of each of those classes. The 

 microscopic aspect of the fume was taken in the nascent stage, and after it had 

 cooled and been exposed to friction in the flues. The fume taken from the interior 

 of the lead flame forms a continuous film on a glass plate, that taken after it has 

 assumed the condition of a white vapour, is granular, and consists chiefly of small 

 isolated round particles. 



4. We studied the chemical character of lead fume with analyses, and the 

 influence of lead and zinc in promoting the volatilisation of silver. 



5. Cooling and friction hasten the deposition of fume in flues. A good arrange- 

 ment of flues is described. 



6. We give a description of the filtering methods, with results of some ex- 

 periments. 



7. We also state the results of a condenser worked at the Wanlockhead Lead 

 Works on the shower-bath principle. This apparatus was highly eulogised in the 

 descriptive catalogue of the Exhibition of 1851 ; since then the company have 

 doubled the quantity of lead saved, by supplementing a long flue, of one mile, to 

 the condenser. 



8. We describe the fourth class of condensers. The requisite conditions to 

 obtain good condensation are to minutely subdivide the smoke current under 

 water, and at the same time use means to neutralise the surface tension of the 

 bubbles ; those conditions are obtained by passing the smoke through a series of 

 wire gauge diaphragms set close together and submerged in water to a depth of 

 seven inches. 



9. The paper concludes with a description of a new process and apparatus on 

 the foregoing principle, assays of smoke before entering and after leaving the con- 

 denser, and general results. 



SATURDAY, AUGUST 23, 1879. 

 The Section did not meet. 



