3 i2 EXPERIMENTAL INVESTIGATIONS. 



sulphuric acid ; with that procured from common zinc and 

 pure sulphuric acid diluted with distilled water ; and with that 

 obtained from distilled zinc and pure diluted sulphuric acid. 

 The contraction was less when the water from which the 

 hydrogen was obtained was carefully purged of air by boiling 

 and the air-pump, but yet there was a notable contraction 

 even when the water had been freed from air to the utmost 

 practicable extent. In the numerous experiments which I 

 made on this subject the contraction varied from the T ^th to 

 the ^V tn f tne whole volume. 



After many fruitless experiments I traced it to a small 

 quantity of oxygen which I found hydrogen to contain under 

 all circumstances in which I examined it. Phosphorus placed 

 in hydrogen, obtained with the utmost care, gives fumes of 

 phosphorous acid, shines in the dark and produces a slight 

 contraction, but there is after this a farther contraction by the 

 use of the ignited wire. 



I may cite the following as an easy experiment and simple 

 illustration of the rapidity with which hydrogen appropriates 

 oxygen. Let hydrogen be collected over water well purged 

 of air ; let a piece of phosphorus remain in it until all com- 

 bustion has ceased, the hydrogen will then be full of phos- 

 phoric vapour ; fill another tube with water, and pass the 

 hydrogen rapidly into it, the second tube will instantly be 

 filled with a dense white fume of phosphorous acid ; the 

 hydrogen having instantly carried with it oxygen from the 

 stratum of water it has passed. 



A very careful experiment was made as follows : Distilled 

 water was boiled for several hours, to this was added one- 

 fortieth part by measure of pure sulphuric acid, and it was 

 cooled under the receiver of an air-pump ; it was now placed 

 in two test-glasses, connected by a narrow inverted tube, full 

 of the same liquid : platinum electrodes were placed in each 

 glass, and the hydrogen caused to ascend immediately into 

 the eudiometer tubes ; the whole was completed within two 

 or three minutes after the water had been removed from the 

 air-pump. Here the ordinary sources of impurity in hydrogen 

 were avoided ; no zinc was used, the sulphuric acid was pure, 

 and the quantity was so small, that, had it not been pure, the 



