15 



88. Gas apparatus, Winkler's. On'stand. Price '21. 10s. 

 1876. Exhibited by J. Orme Sf Co. 



89. Apparatus for experimenting with liquid sul- 

 phurous acid. 



Made by Warmbrunn, Quilitz, Sf Co., Berlin. 

 B. 176. 1877. 



90. Graduated Nessler tube with tap in side arm near 

 bottom. Price 5s. Nessler tubes (three), two plain, the 

 other marked at 50 c.c.'s. Prices \0d. and Is. Stand, 

 black wood, for use in Nessler's test. Price 3s. 6d. 



1886. Exhibited by Townson Mercer. 



Nessler's test is a very delicate method of detecting or 

 estimating very small quantities of ammonia. Nessler's solution 

 is made as follows : 35 grams KI are dissolved in 120 c.c. of 

 water, 5 c.c. of it transferred to a beaker and the remainder 

 added to a concentrated solution of mercuric chloride until the 

 precipitate which forms ceases to be redissolved, some of the 

 5 c.c. of potassium iodide removed is added until the precipitate 

 just redissolves, then an aqueous solution of JOO grains of 

 caustic potash in 200 c.c. of water is added and the mixture is 

 diluted to 500 c.c. This solution when added to water containing 

 traces of ammonia or ammoniacal salts gives a yellow or brown 

 colouration. The tint produced by adding 1 c.c. of Nessler's 

 solution to 50 c.c. of the water containing traces of ammonia 

 is compared with the tint produced from water containing a 

 known quantity of ammonium chloride, and when after trial 

 these tints have been obtained of the same intensity tlie amount 

 of ammonia to be estimated is known. 



91. Apparatus for simultaneous production of hydro- 

 gen, carbonic acid, and sulphuretted hydrogen. 



Presented by P. Waage, Professor of Chemistry and 

 Director of the Chemical Laboratory at the Royal University 

 of Ghristiania, Norway. 



E. 487. 1877. 



The apparatus consists of a reservoir for hydrochloric acid of 

 10-15 per cent, strength. At the bottom of this reservoir are 

 three apertures through which it is connected in the usual 

 manner by glass tubes and stopcocks with three cylindrical 

 jars, one filled with zinc, the second with marble, and the third 

 with sulphide of iron. Beneath each of these, and communi- 

 cating with the sewers, is another reservoir into which the 

 solutions of chlorides are gathered. The three gases generated 

 are conducted through wash bottles furnished with stopcocks of 

 glass ; when these are turned off the several gases and the 



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