LEEDS chemists’ ASSOCIATION. 
451 
iodine being greatly superior to the shore weed. About twenty-two tons of wet sea¬ 
weed, when dried and burnt, yield a ton of kelp, and the crude potash salts of this 
amount to eight or nine hundredweight, being a mixture of potassic sulphate, chloride, 
and carbonate, with some sodic admixture. These products are used for the manufac¬ 
ture of prussiate of potash, and of saltpetre from nitrate of sodium. The most 
thorough change in the method of treating seaweeds for the manufacture of iodine and 
its 9 ,llied products is that of my friend Mr. Stanford, which received the distinction of a 
medal in 1862. Mr. Stanford aims at avoiding the waste of half the iodine, and many 
other principles which occur in the ordinary method of burning the weeds, and to 
accomplish this he dries and compresses them, and effects their destructive distillation in 
retorts, as in the production of coal-gas. Various hydrocarbons, naphtha, acetic acid, 
ammonia, etc. are obtained in addition to much larger quantities of iodine and bromine 
than would be got by the old method, whilst the fixed mineral salts, including the 
potassic ones, are, of course, amongst the assets. 
4th. Potash salts of direct mineral origin .—In the year 1860, 160 tons of potash 
salts from a direct mineral source were raised and applied chiefly to agriculture. This 
was due to the discovery of veins of mixed potassic salts overlying a bed of common 
salt at Stassfurt, near Magdeburg, in Prussia. Both the chlorides of potassium and 
magnesium are present in the salt. The position of this deposit in relation to the bed 
below is of great interest, indicating by the order of superposition found the order in 
which the salts of sea-water would be deposited by gradual concentration, viz. the bulk 
of the sodic chloride falling first, then a mixture of the same, with earthy sulphates and 
some magnesic and potassic chlorides, whilst the bulk of the two salts last named would 
be deposited at the top. The natural inference is, of course, that potash-beds may exist 
above other salt-beds.* 
5th. Potash from sea-ivater. —M. Balard, who discovered bromium more than forty 
years ago, has devoted his energies to the problem of extracting potash salts from sea¬ 
water, and his efforts have been crowned with so much success that M. Merle, who has 
extended them, received a medal at the Exhibition of 1862. The salts of soda in sea¬ 
water exceed those of potash in the ratio of sixteen to one, and this fact will doubtless 
act as a barrier to the extensive production of the latter salts from this source. Besides 
the new sources of potash now enumerated, some very promising experiments have 
been made for its extraction from felspar. 
The moral to be drawn from these various attemps to ransack the stores of nature for 
this valuable alkali appears to be the following, viz. that when depending upon vita¬ 
lized agencies such as vegetables, our powers of production are limited by the slow and 
gradual character of growth of such agents. If we rely upon the forest tree to abstract 
from the soil, by its countless rootlets, minute quantities of potash, and store them up for 
our use, or, again, upon the seaweed to separate from sea-water, by some marvellous 
power of selection (of the nature of which we know nothing), its potash, which 
in the water exists in the ratio of one to sixteen of soda, but which in the plant 
will be as one to three of soda, we must wait patiently whilst trees and seaweeds grow. 
The same truth applies to all other vegetable productions, as, for instance, dye-wares. 
But observe the difference when we apply to the mineral kingdom for such products 
* Analyses of Potassic Salts from Stassfurt. 
No. 1. 
Chloride of Potassium.50-55 
Chloride of Sodium.40-45 
Chloride of Magnesium, moisture, etc. . 
100-00 
No. 2. 
Sulphate of Potassium.18-20 
Sulphate of Magnesium.18-20 
Sulphate of Calcium.3-50 
Chloride of Sodium.40-40 
Chloride of Magnesium.3-40 
Magnesia.2-30 
Moisture, etc. 14'0Q 
100-00 
