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ADDITIONAL CHEMICAL EXAMINATIONS. 



The mineral from which this earth was extracted differs from talc, in the absence of any foliated struc- 

 ture ; in not exfoliating before the blow-pipe j in giving off water in the matrass, which talc does not, 

 being quite anhydrous, while this is a hydrated silicate. It contains twenty per cent, less silica than 

 talc. 



Leaving out of account the earth in question, the chemical constitution of this mineral comes nearest 

 to saponite and soapstone. The specimens of saponite or soapstone analyzed by Klaproth, contain three 

 to four per cent, more silica; four to five per cent, more magnesia; four to five more alumina, and about 

 the same quantity of water and oxide of iron. 



The specimens of saponite from Brusksveden, analyzed by Svanberg, contain eight to nine per cent, 

 more silica ; twenty-two per cent, more alumina, and ten per cent, less magnesia, and eight per cent, 

 less water. 



From the green earth often disseminated in the Italian amygdaloids it differs essentially. Most of 

 these contain a large percentage of oxide of iron, and very little magnesia — two to six per cent. only. 

 Several of the analyses of Serpentine and Mermolite indicate nearly the same amount of silica as in this 

 mineral, but in them the magnesia is doubled. 



Some specimens yielded a fraction of one per cent, of copper, but this is an accidental impurity, like 

 the adhering carbonate; the acid solution of the pure mineral gives with sulphuretted hydrogen a slight 

 milkiness only from a trace of precipitated sulphur, caused by the reduction of the small quantity 

 of peroxide of iron present. The green colour of the mineral may probably be attributed to the 

 presence of this peculiar earth, which produces green salts. 



In consequence of the difficulty in separating the traces of magnesia, without dissolving part of the 

 earth itself, I have not been able to ascertain the exact percentage of the earth in the mineral, nor yet 

 determine its combining proportion. 



From the quantity of chlorine evolved during the solution of the mineral and the earth in hydrochloric 

 acid, it appears that this earth must exist in at least two degrees of oxidation : the chlorine being dis- 

 engaged, just as in the case of the solution of the higher oxides of manganese* when treated with hydro- 

 chloric acid. 



If the small percentage of alumina and oxide of iron present be regarded as accidental, it is probable 

 that the constitution of the mineral is : 



Two equivalents of bisilicate of magnesia and one equivalent of the peroxide of the earth, with two 

 equivalents of water : or, 



2 Mg Si 2 +NE, Si+2H. 



Although most of the water is expelled by a heat below redness, still I think it must be regarded as 

 almost all combined ; since the quantity obtained is very uniform, and is within a fraction of a per cent, 

 of two equivalents. 



From the above, I conclude that the earth contained in the mineral, which is but slightly soluble in sal 

 ammoniac, insoluble in caustic potash, and producing the above reaction with reagents, and green and 

 yellow salts, must either be a new earth, or else a modification of some known earth not previously 

 noticed. 



The name Thalium is proposed for the base of this earth, Thalia for the earth itself, and Thalite for 

 the mineral from which it is extracted. 



In 1849, Dr. Shumard brought a soft, brittle, pale green mineral, which was collected from the cavities 

 of an amygdaloid, three miles above Kettle River, in Minnesota, which has, when dried, much the appear- 

 ance and consistence of this silicate of magnesia from Lake Superior. This Kettle River mineral, when 

 first collected, was as soft as butter, but hardened by exposure. 



I also made an analysis of this mineral, but found it to contain a much smaller quantity of magnesia, 

 a much larger percentage of alumina, more silica, and none of this peculiar earth. The constituents are 

 as follows : 



Silica, ..... 52-7 

 Matter insoluble in HC1, being silicates of | N Alumina, with a trace of oxide of iron, . 20-0 

 alumina, magnesia, and alkali, 85-2, | <j Mngncsiaf 4 . 35 



Alkali and loss, .... 8-15 



* The mere trace of manganese present in the mineral will not account for the quantity of chlorine evolved. 



