4 THOMAS MACFAELANE: 



not wholly remove the arsenic, and it is necessary to purify the acid by bringing it into 

 contact with sulphuretted hydrogen. This gas is not, however, transmitted through the 

 acid, but the latter having a strength of 50° Beaume, is allowed to drop down through an 

 atmosphere of the gas contained in high leaden towers, filled with prisms which are 

 made of sheet lead, and so placed as to divide and distribute the acid in the state of spray, 

 which is then more readily acted on by the gas. The iirecipitated sulphide of arsenic is 

 removed from the acid by means of vacuum filters. When the difficulty of handling- 

 sulphuretted hydrogen is considered, it is not to be wondered at that this process is not to 

 be found in operation elsewhere, and it may safely be said that it could only be carried 

 into practice under the pressure of direst necessity. I think it may be said that for her 

 preservation, Freiberg is largely indebted to Freiherr a'ou Beust, who was Oberberghaupt- 

 mann, at the time when measures were taken to utilise the furnace fumes. 



The picture of the Freiberg smelting establishments and the A^erdant fields and forests 

 round them may be compared with Swansea and its environs, greatly to the disadvantage 

 of the latter. One of the fairest landscapes in England there lies desolate, because no 

 overwhelming pressure has been brought to bear upon the smelters to utilise their waste 

 gases. Nor is there the remotest likelihood of this being done until the pyrites mines of 

 Spain are exhausted. 



I well remember to have seen, as a boy, the " pillar of fire by night," which stood 

 over each of the great iron works of the valley of the Clyde. Those fires are paling now 

 and the work of utilising their waste gases with their nitrogenous constituents has 

 made very wonderful progress. In fact, the task was accomplished at seven of the furnaces 

 of the Gartsherrie Iron Works when I visited them in 1884. Instead of allowing the 

 gases to blaze into the atmosphere at the tunnel head of each furnace, they are confined 

 there, withdrawn by means of huge exhausting machines, and subjected to the same cooling 

 and condensing processes which crude illuminating gas undergoes in gas works, after it 

 leaves the retorts. But while common gas, as it issues from these, never exceeds 200° 

 Fahr. and seldom averages more than 135°, the furnace gases have to be cooled down 

 from a temperature of "ZOO", and it is also to be remembered that the condensing appa- 

 ratus for the latter is of colossal dimensions compared with that of gas works. Instead of 

 an hydraulic main 18 in. in diameter above the retorts, large tubes *7 and 9 feet in diameter 

 have to be employed at the blast furnaces. By passing the gases from these through a 

 system of atmospherical coolers containing 200 vertical pipes, each 40 feet long and 2J 

 feet wide, their temperature is reduced to 100° Fahr. It is further reduced to 65° by 

 bringing the gases into contact with an hydraulic condenser containing no less than nine 

 miles of three-inch pipes in which the water circulates. The gases now p ass into a large 

 tower or " scrubber " 75 feet high and 25 feet square, where they are met by a descending 

 shower of water which dissolves the ammonia and washes out the tar. On arriving at 

 the top of this tower, the gases descend a large tube and enter into another scrubber 

 similar to the first one, but only 60 feet high, where another shower of descending water 

 is met and the last trace of ammonia and tar is removed. The gases thus purified are at 

 last utilised as fuel, part being used for raising steam, part for working the ammonia 

 stills, while a third portion is used for heating the blast for the iron furnaces. The treat- 

 ment of the tar and ammoniacal liquor, being similar to that of the same products in gas 

 works, need not be described. The increased production of sulphate of ammonia from 



