11 



To fill the bottles wit It x/</Hf A ////. 



Open the cock on the bent tube, close the top of the compari- 

 son tube with a cork or the finger. Then hold tin- standard in 

 a little beaker, so that the bent tube dips into it, and draw up 

 the syringe, when the liquid will at once rush into thr bottlr. 



To nxiL'r (/' comparison. 



Turn ott' the tap of the bent tube, remove the 'cork or finger 

 from the comparison tube, and force the liquid up till tin- depth 

 of tint, as shown by the mirror at the top, is equal to that of 

 the 20 divisions of liquid being tested. 



Read oft' the height of the column on the scale. 



Number of division* <>f *! nda i'<l x pr ,-<-,> ntage of standard 



20 

 = Per cent. 



To empty out old standard. 



Close the top of the comparison tube, open the tap of the 

 blow-out tube, and force the liquid out of the bottle by pressing 

 down the syringe. 



To dean out the bottles. 



When a new standard is to be used it is better, after emptying 

 the bottle as completely as possible, to suck a little of the new 

 standard in and force it out again. 



If necessary, from time to time, the bottles can be cleaned out 

 in the same way with dilute HC1 and water. 



2. MODELS AND DRAWINGS SHOWING THE CONSTRUCTION 

 OF FURNACES USED IN METALLURGICAL OPERATIONS. 



18. Model of a blast furnace, with open breast, from 

 the series of models intended for technical instruction. 



E. 129. 1868. Made by J. Schroeder, Darmstadt. 



19. Model of a blast furnace, with closed breast, from 

 the series of models intended for technical instruction. 



E. 130. 1868. Made by J. Schroeder, Darmstadt. 



20. Model of a blast furnace boiler, upon elastic 

 supports. 



1876. Lent by Jeremiah Head, M.I.C. E. 



Long plain cylinder boilers, when hung as ordinarily upon 

 rigid supports, are found to rise clear of the latter at their ends 

 when in use, and in the middle when out of use. This leads to 

 seam rips, and frequently explosion. By turning the small 



