162 On Iodine. 
nascent sulphuretted hydrogen of the latter; their atoms of oxy- 
gen and hydrogen uniting to form water, while the sulphur of 
both is precipitated. I cannot in any other way account for the 
very copious separation of sulphur, while very little sulphuretted 
hydrogen appears. From the excess of sulphite present in the 
‘liquid, we have a redundant quantity of sulphurous acid evolved. 
From eight liquid ounces, equal by weight to cleven, 213 grains 
of sulphur are obtained. 
The liquid saturated with the sulphuric acid has a specific 
gravity of 1°443, a bright yellow colour, and it does not affect 
the purple infusion of red cabbage. I distilled eight ounces of 
this in a glass retort. The stopper of the tubulated receiver 
was frequently blown out by the escape of incondensable gas, even 
after the liquid had been for a long time in ebullition. This, 
which was probably hydriodie acid gas, continued to be evolved 
to the very last. In the receiver, which had been kept very 
cool, a colourless and nearly transparent liquid was found. Its 
specific gravity was 1:054, of an acidulous and acerb taste ; it 
reddened vegetable blues, and powerfully blackened brass. 
From this liquid I could extract only three or four grains of 
iodine, though the viscid black substance left in the retort yielded 
more than twenty times the quantity. We see therefore that by 
distillation very little hydriodic acid can be procured from the 
saturated liquid. 
_ Inthe prosecution of my researches to ascertain the best mode 
of extracting the iodine, I at length discovered the causes of the 
anomalous results which had not a little perplexed me at first, 
rendering the product very uncertain. The following method 
was found to answer extremely well. ‘ 
The brown iodic liquid of the soap-boiler was heated to about 
230° Fahr.; poured into a large stone-ware bason, of which it 
filled nearly one-half, and was then saturated by the proper 
quantity of sulphuric acid, as above stated. The acid ought to 
be previously diluted with its own bulk of water*. On cooling 
the mixture, a large quantity of saline crystals is found adhering 
to the sides and bottom of the vessel. These are chiefly sulphate 
of soda, with a very little sulphate of potash, and a few beautiful 
oblong rhomboidal plates of hydriodate of soda. The precipi- 
tated sulphur is intermixed with these crystals. 
After filtering the cold liquid through woollen cloth, I add to 
every twelve ounces apothecaries’ measure, 1000 grains of pow- 
dered black oxide of manganese. This mixture is made in 4 
glass globe or matrass, over the mouth of which a glass globe is 
* When concentrated oil of vitriol is added, the effervescence is very 
violent; the liquid reddens wherever the acid falls, and a little of the pur- 
ple vapour of iodine rises, 
then 
