962 



SULPHURIC ACID 



2(HO.SO S ) 



Sulphuric acid. 

 2H 2 SO< 



Sulphur. 

 + S 



3S0 2 + 



Sulphurous acid gas. 



380" + 



2HO. 



Water. 

 2H O. 



1946 



2nd. If there is not a sufficient quantity of steam admitted into the chamber, the 

 solid compound of sulphuric acid and binoxide of nitrogen, above mentioned, -would 

 be formed on the sides of the chamber, and thus remove the oxidising agent from 

 action, and hence a large quantity of sulphurous acid would escape by the waste-pipe 

 unchanged. 



3rd. A deficiency of nitric acid in the chamber also causes great loss ; the sul- 

 phurous acid, as in'the former case, escaping unoxidised. 



The first of these three subjects was counteracted by M. Grovelle, who, taking 

 advantage of an idea put forth by M. Clement Desormes, constructed a furnace for 

 burning the sulphur, so as to have a double current of air. He substituted for the 

 sole of the furnace some parallel bars of iron, on which were placed cast-iron pans or 

 boxes, bound together, but leaving intervals for the entrance of air between each : 

 these were filled with sulphur, which was then ignited, and thus a plentiful supply of 

 air was constantly kept up. 



The reactions which take place in the sulphuric-acid chamber have recently been 

 studied by Mr. H. A. Smith, who concludes, contrary to generally-received opinions, 

 that under certain circumstances action can take place between dry sulphurous acid 

 and nitric-acid gases without the intervention of steam. He believes that the best 

 form of chamber should be long and not high, having, in fact, the following dimen- 

 sions : length 150 feet, width 95 to 30 feet, and height 10 to 12 feet. The tempera- 

 ture should be kept as nearly as possible at 200 Fahr., and in starting the chamber 

 he recommends that sulphuric acid should be run on the bottom in preference to 

 water. See 'The Chemistry of Sulphuric Acid Manufacture,' by H. A. Smith, 1873. 

 Fuming, or Nordhausen Sulphuric Acid. At Nordhausen and other parts of Saxony, 

 sulphuric acid continues to be made upon the old 

 plan. This consists in first subjecting sulphate 

 of iron, or green vitriol, to a gentle heat, by which 

 it is deprived of its water of crystallisation ; it 

 is then distilled in earthenware, tubular, or pear- 

 shaped retorts, of which a large number are placed 

 in a gallery-furnace. Fig.. 1946 shows the fireplace ; 

 abb, chamber on each side of the fireplace, for 

 depriving the green vitrol, c c, of its water. 



To these retorts are adapted earthenware re- 

 ceivers, into which some ordinary sulphuric acid 

 is previously placed, to condense all the anhydrous 

 sulphuric acid which comes over. The heat is 

 raised gradually, and at last the retorts are subjected to an intense heat, which is kept 

 up for several hours. 



Some sulphurous acid gas escapes, arising from the decomposition of some of the 

 sulphuric acid of the sulphate by the oxide of iron, and nothing remains in the retorts 

 but sesquioxide of iron. 



Anhydrous Sulphuric Add, or Sulphuric Anhydride. This is most easily obtained by 

 subjecting the Nordhausen sulphuric acid to a gentle heat in a glass retort, to which 

 is adapted a dry receiver placed in ice. White fumes of anhydrous sulphuric acid 

 come over and are condensed in the receiver. Care must be taken to avoid water 

 coming into contact with it, as it unites with it with some violence. 



It is best to have a receiver which can be hermetically sealed as soon as the opera- 

 tion is completed. 



Properties of the different Sulphuric Acids. 



Anhydrous Sulphuric Add, or Sulphuric Anhydride. (SO'.) This is a white cry- 

 stalline body, very much resembling asbestos in appearance. Exposed to the air, 

 some of it absorbs moisture, and the rest flies off in white fumes. Dropped into water 

 it produces a hissing noise, just like red-hot iron, and in largo quantities causes ex- 

 plosion. It melts at 66 Fahr., and boils at about 120 Fahr. The sp. gr. of tho 

 liquid, at 78 Fahr., is 1-97 (Pereira), and that of its vapour 3'0 (MitscherUch). It 

 does not present acid properties unless moisture be present. 



Nordhausen Sulphuric Acid. HO.S0 3 ,SO S (H'SO'SO 8 ). This is an oily liquid, gene- 

 rally of a brown colour (from some organic matter), which gives off white fumes of 

 anhydrous sulphuric acid when exposed to the air. Its sp. gr. is about 1 -9. It is 



