212 SCIENTIFIC APPARATUS. 



same size as the eudiometer, and containing some air, which, 

 before each measurement, is brought to the same volume by raising 

 or depressing the tube in the trough ; the eudiometer is then 

 raised or lowered until the top of the mercury is at the same level 

 as that in the pressure tube: the reading is then made. Liquid 

 re-agents are introduced into the eudiometer by means of a 

 syringe, and when the absorption is complete they are removed 

 by a plug of moistened cotton-wool attached to the end of a steel 

 vrire. 



In Frankland and Armstrong's system of water analysis, the 

 gaseous products of the combustion of the organic matter in the 

 water residue are measured and analyzed in a simple gas analysis 

 apparatus, similar in principle to that of Regnault and Reiser, 



Of the apparatus and materials used in chemical research, 

 thown in the present Exhibition, some of the most interesting 

 and important are the following. Dr. Andrews and Professor 

 Tait exhibit a complete set of apparatus employed in their inves- 

 tigations on the nature and properties of ozone. Soret's instru- 

 ment, by which the constitution of this body was determined, and 

 also Sir Benjamin Brodie's apparatus, are shown. Professor Ros- 

 coe contributes a large collection of the compounds of vanadium, 

 an element which he has lately submitted to very thorough inves- 

 tigation, many of his results being of considerable value in the 

 theory of chemistry. Professor Schorlemmer's investigations on 

 the hydrocarbons of petroleum are illustrated by specimens. 

 Mr. Perkins contributes an interesting collection illustrating his 

 researches, among which may be specially noted those connected 

 with the synthesis of coumarine. Dr. Frankland exhibits a very 

 large collection of organic compounds obtained during his 

 researches. A considerable number of bodies prepared at the 

 University of Edinburgh by Professor Crum-Brown, Dr. Letts, 

 and their pupils, during their investigations on the addition- 

 products of sulphide of methyl, hyposulphites, &c., are shown. 

 The Fellows of the German Chemical Society have combined m 



