f 161-] 
XXIV. On Iodine. By Anprew Ure, M.D. Professor of 
Chemistry, &c. Se., Glasgow, 
To Mr. Tilloch. 
Sir, — Due great trouble and uncertainty attending all the 
processes which have been prescribed in the scientific journals 
for procuring this interesting elementary body, and the high 
price at which it is sold in Great Britain, induced me about two 
years ago to inquire whether an easier and cheaper mode of 
preparing it might not be discovered*. 
As many of the Scotch soap manufacturers use scarcely any 
other alkaline matter for their hard soaps except kelp, it oc- 
curred to me that in some of their residuums a substance might 
he found, rich in iodine. Accordingly, after some investigation, 
I found a brown liquid of an oily consistence, from which I ex- 
pected to procure what I wanted. ‘his liquid drains from the 
salt, which they boil up and evaporate to dryness from their 
waste leys fer the soda manufacturer. I instituted a series of 
experiments on the best mode of extracting the iodine. As these 
succeeded far beyond my expectation, I hope the following ac- 
count of them will prove not uninteresting to the British chemist. 
The specific gravity of the above liquid, as obtained at different 
times, is very uniformly about 1-374, water being 1:000. It 
converts vegetable blues to green, thus indicating free alkali. 
Of this the manufacturer is aware, for he returns it occasionally 
into his kelp leys. Its boiling point is 283° Fahr. Eight ounces 
apothecaries’ measure require precisely one measured ounce of 
sulphuric acid for their neutralization. Supposing this quantity 
of acid combined with soda, it would indicate one part of pure 
soda in eleven by weight of the liquid. But the greater part of 
the alkali is not uncombined; for an immense quantity of sul- 
phurous acid and a little sulphuretted hydrogen gases escape on 
the affusion of the sulphuric acid. One hundred grains of the liquid 
yield 3-8 cubic inches of gas, chiefly sulphurous acid; and sul- 
phur is at the same time deposited. From the quantity of sul~ 
phur, one might expect a larger proportion of sulphuretted hydro- 
gen; but the disengaged gas possesses the peculiar smell and 
pungency of burning sulphur, blanches the petals of the red 
rose, but. shows hardly any action on paper dipped in saturnine 
solutions. Iu the instant of decomposition of the sulphite of so- 
da, and hydroguretted sulphuret existing in the liquid, the nascent 
sulphurous acid of the former may be supposed to act on the 
* The iodine sold in London is for the most part imported from Paris, 
as I was informed’ by an-eminent practical chemist. 
,_ Val. 50. No. 233. Sept. 1817. L nascent 
