380 



SCIENTIFIC RECREATIONS. 



combination with water, sulphurous and sulphuric, and some others, which, 

 as in the case of nitrogen, form a series of multiple proportions, the oxygen 

 being present in an increasing regularity of progression, as follows : 



Name of Acid. 



Hypo-sulphurous acid 



Sulphurous acid . -,,' 



Sulphuric acid . 



Thio-sulphuric, or hypo-sulphuric acid 



Dithionic acid 



Trithionic acid . ' . , 

 Tetrathionic acid '.. 

 Pentathionic acid 



Chemical Formula. 



. H 2 S0 2 



. H 2 SO 3 



. H,S0 4 



. H,S 2 3 



. H 2 S 2 G 



' H 2 S 3 3 



. H 2 S 4 G 



C . H 2 S 5 6 



The last four are termed "polythionic," because the proportions of sulphur 

 vary with constant proportions of the other constituents. 



Fig. 38 . .Liquefaction ol sulphuric acid. 



The sulphurous anhydride mentioned above is produced when we burn 

 sulphur in the air, or in oxygen ; it may be obtained in other ways. It is a 

 colourless gas, and when subjected to pressure may be liquified, and crystal- 

 lized at very low temperature. It was formerly called sulphuric acid. It 



is a powerful "reducing agent," and a good anti- 

 septi:. It dissolves in water, and forms the 

 H 2 SO 3 , now known as sulphurous acid. 



Sulphuric acid is a most dangerous agent 

 in wicked or inexperienced hands, and amateurs 

 should be very careful when dealing with it. It 

 takes the water from the moist air, and from 

 vegetable and animal substances. It carbonizes 



Fig. 3 c 4 . -Retorts ;nd receivers for and destroys all animal tissues. Its discovery 



is due to Basil Valentine, in 1440. He dis- 

 tilled sulphate of iron, or green vitriol, and the result was " oil of vitriol." 

 It is still manufactured in this way in the Hartz district, and the acid 

 passes by retorts into receivers. The earthen retorts, A, are arranged 



