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The following paper was read, 
On the Reduction of Sulphuric Acid by Zinc-Amalgam. 
BY Unk VW Az, 
Although, as is well known, a number of oxidizing agents 
are capable of oxidizing sulphuretted hydrogen to sulphuric 
acid, the reverse reaction, viz., the reduction of sulphuric 
acid to sulphuretted hydrogen, has hitherto been observed 
only in a few cases, and even then only to a very limited 
extent. Messrs. Calvert & Johnson published in 1866 some 
observations upon the action of zinc upon the various hydrates 
of sulphurie acid, in which they remark that at a high tem- 
perature, the mono-, bi-, and ter-hydrates of sulphuric acid, 
when acting upon zine, evolve principally sulphurous acid, 
while the fourth, fifth, and sixth hydrates are acted upon (in 
the words of the Jahresbericht) “with a preponderating 
evolution of sulphuretted hydrogen,” an observation which I 
can confirm if it is intended to say that more H2S is formed’ 
than SO2, but less than H, as on repeating the experiment I 
found that but very little H:S was formed. According to. 
Messrs. Calvert & Johnson, sulphuric acid which is diluted’ 
with more than six equivalents of water, evolves pure: 
hydrogen, an observation which was disproved by Kolbe, 
who showed that when even chemically pure dilute sulphuric: 
acid acts upon chemically pure zine, a trace of sulphuretted 
hydrogen is always formed. In the majority of reactions,. 
however, in which a reduction of sulphuric acid takes place, 
it stops at sulphurous acid, as when mercury, copper, carbon, 
etc., act upon the acid. Oppenheim has shown that whem 
concentrated sulphuric acid and phosphorus act upon each: 
other the result is phosphorous and anhydrous sulphurous: 
acid, according to the formula 8SO,H,+2P = 2PO;H; +8S0Os2.. 
I have lately studied the action of zine and sodium 
amalgam on concentrated sulphuric acid, and have made: 
the—in view of the foregoing remarks—somewhat unexpect-. 
ed observation, that in this case a considerable amount of 
PROC. LYC. NAT. HIST. N. Y.—VOL. 1 10 
