Sulphuric Acid-manufacture. 123 



These thermometers were lowered into the chamber at the 

 different points by long " threads " of lead and allowed to re- 

 main for about two hours, the yield of vitriol and general appear- 

 ance of the chamber being carefully noted each day. The results 

 obtained by this investigation have been very completely borne 

 out by those already shown in Section III., which, although I 

 considered their proper place in the paper to be before the pre- 

 sent section, nevertheless came later in the course of investigation. 



As in a former case, I divided the chamber into separate parts, 

 so that I could have some definite plan of procedure. In this 

 case the chamber was divided along its length at four heights, 

 thus — 



1st, at the height of 24 feet from bottom of chamber, 

 ^ fl d, „ „ lo „ „ „ „ 



^ ro -? 3i >} " )> )> a )) 



**tn, ,, „ o ,, „ „ „ 



the temperature being taken every 10 feet along the length at 

 these heights. 



In looking at Diagram I. the first thing that strikes us is the 

 very sudden fall in temperature which takes place in passing from 

 10 feet from the end of chamber (at the entrance) to 20 feet, there 

 being a fall here of 87° F. After this the temperature is compa- 

 ratively constant till it reaches 110 feet from end, when it again 

 falls continually till it reaches 113° F., at which temperature 

 the gas passes from the chamber. This is that portion of the 

 chamber which I have previously called the " reservoir/' and in 

 which very little, if any, action between the gases takes place ; 

 and it is worthy of notice that, with the exception of the first ten 

 feet, at no place in this portion does the temperature rise above 

 130° F. And if we turn to the previous section of this paper, 

 we find that in exp. II. the nearest approach to this temperature 

 is 122°*8 F. ; and here we have the remark, " ruddy fumes begin 

 to disappear." Here, then, is another proof, if another were 

 required, that the upper part of the lead chamber is not of use 

 as a condensing " space," but merely as a reservoir for containing 

 the gases, and, if necessary, assisting proper mixture. 



In this diagram we may see also the points in the chamber at 

 which steam is thrown in. At 40 feet and at 70 and 110 feet 

 respectively we have decided falls of temperature, these being 

 very nearly the places of the steam-pipes. The high tempera- 

 ture at the beginning may be accounted for by the fact that 

 shortly below this the pipe by which the gases are conducted to 

 the chamber is inserted. 



