] 872.] Mr. W. Crookes on the Atomic Weight of Thallium. 4*75 



Similar experiments made with oil of turpentine entirely confirmed the 

 view of Soret as to the amount of contraction which the gas undergoes 

 when acted upon by this substance, the mean of eight experiments giving 

 2 '02 as the value of the contraction. 



The investigation of the effect due to the action of the electrized gas upon 

 protochloride of tin is attended with considerable difficulty, from the cir- 

 cumstance that a solution of protochloride of tin is readily oxidized by the 

 action of pure oxygen. The difficulty was met in two ways, both of which 

 led to the same conclusion, — namely, by applying a correction for the oxi- 

 dation effected by the oxygen with which the ozone was associated, and by 

 using very dilute solutions of the protochloride of tin in which this oxi- 

 dation is reduced to a minimum. In two experiments conducted on the 

 latter principle, and in which the oxidation, as well as the contraction, was 

 experimentally determined, the value of the contraction was found to be 

 2*19 and 2'33, while the oxidation in the two experiments respectively was 

 3-12 and 3-07. 



Using the notation employed by the author in a previous communication * 

 to the Royal Society, and putting £ 2 as the symbol of the unit (that is of 

 l'OOO cub. centim. at 0° and 760 millims.) of oxygen, and putting [£] as the 

 symbol of that simple weight £ transferred to the oxidized substance in the 

 various oxidations effected by the ozone, and further assuming that ozone 

 is to be regarded as some denser form of oxygen, to the unit of which the 

 symbol £ 2+w (where n is a positive integer) is to be assigned, the result 

 of the total system of experiments of which the account is given in this 

 memoir may be expressed, so far as regards the distribution of the matter 

 of the unit of the ozone, in the various reactions by the general equation 



(p + q)k 2+n = q¥ + (p(2 + n) + qn) [£], 

 where p s q> n are positive integers. 



The investigation of the various hypotheses originating in this equation 

 leads to the conclusion that the hypothesis that the unit of ozone is com- 

 posed of three simple weights, £, and is to be symbolized as £ 3 , is both ne- 

 cessary and sufficient for the explanation of the total system of phenomena, 

 and that no other hypothesis of the order referred to is tenable. 



XVI. " Researches on the Atomic Weight of Thallium." By William 

 Cuookes, F.R.S. &c. Received June 38, 1872. 



(Abstract.) 



In June 1862, and in February 1863, 1 had the honour to lay before the 

 Royal Society communications on the subject of the then newly discovered 

 metal, thallium. In these I gave an account of its occurrence, distribution, 

 and the method of extraction from the ore, together with its physical 



* Vide " Calculus of Chemical Operations," by Sir B. C. Brodie, Bart., F.R.S,, 

 Phil. Trans. 1866, pp. 781-859. 



