76 CHEMICAL DISCOVERY AND INVENTION 



CHAPTER III 



APPARATUS 



ON entering a chemical laboratory the first impression on the 

 mind of a visitor not conversant with the science of chemistry 

 and its practice is produced by the apparently innumerable 

 ranks of bottles. This is particularly noticeable in those labora- 

 tories in which provision is made for a large number of students, 

 inasmuch as each worker requires for his individual use a con- 

 siderable number (about thirty) of " reagents," liquid or solid, 

 which are so frequently in use that it would be a source of great 

 inconvenience if they were shared with a neighbour. Beside 

 these there are usually stacks of shelves placed in a position of 

 easy access, so that the bottles of solutions or other materials 

 which are in less frequent demand may be ready for common 

 use by any of the occupants of the laboratory. 



Laboratories which are devoted to other purposes than the 

 teaching of bodies of students do not generally display so 

 prominently any large array of bottles. By reference to some 

 of the illustrations which show the interior of laboratories 

 employed for special purposes it will be seen that bottles do not 

 always form a conspicuous feature. In such cases apparatus 

 connected with the special business of the laboratory will catch 

 the eye. It may be apparatus for distillation, for the estimation 

 of melting points or freezing points, for electrolytic or other 

 electrical operations, and so forth ; in any case glass vessels of 

 all shapes and sizes, glass tubes contorted into a variety of 

 forms, and the appearance of the Bunsen blue cone of burning 

 gas at many places will be prominent features of the chemical 

 laboratory. 



Detailed descriptions of apparatus would alone occupy a 

 large volume, and since the purpose of this book is general no 

 attempt will be made to describe apparatus which has long been 

 a familiar part of the indispensable equipment, 



Weighing. Every chemist must possess at least one balance 

 of precision which will carry 100 to 200 grams in each scale and 

 turn with a difference of T Vth milligram. With the same instru- 

 ment, however, and a smaller mass in the pan, and using the 



