312 
TOPULAR SCIENCE REVIEW. 
Society recently, Professor Roscoe gave an elaborate account of his investi- 
gations into the chemistry of this element. Professor Roscoe, it seems, has 
proved that the substance supposed by Berzelius to be vanadium, is not the 
metal, but an oxide, and that the true atomic weight of the metal is 51-3. 
The vanadic acid, V0 3 , of Berzelius, hence, becomes V 2 0 5 , corresponding to 
P 3 0 5 and As 2 0 5 ; and the above-mentioned isomorphism is fully explained. 
The suboxide of Berzelius is a tri-oxide, V 2 0 3 ; whilst the terchloride (VC1 3 ) 
of Berzelius is an oxychloride, VOCl 3 , corresponding to oxychloride of 
phosphorus, P001 3 . Professor Roscoe has succeeded in obtaining bromine 
and iodine compounds of vanadium, and also various metallic vanadates. 
In the course of his lecture he pointed out that the characters of the vana- 
dates bear out the analogy of the vanadic acid with the highest oxides of 
phosphorus and arsenic ; and stated, in conclusion, that vanadium, hitherto 
standing in no definite relation to other elements, must now be regarded as 
a member of the well-known triad class of elementary substances, com- 
prising nitrogen, phosphorus, boron, arsenic, antimony, and bismuth. 
Transformation of Isatine into Indigo. — At the meeting of the Chemical 
Society of Berlin on May 23, Herren Baeyer and Emmerling reported their 
researches on the transformation of isatine into indigo. As isatine, when 
treated with nascent hydrogen, unites with it and forms indol, a substance 
not capable of uniting with the reduced substance was sought for, and dis- 
covered in phosphorus, the solvent employed being chloride of acetyle or 
of phosphorus. Real indigo-blue and indigo-red were thus produced. 
The latter stands in the same relation to the blue as purpurine does to aliza- 
rine. To complete the long hoped-for discovery of producing artificial 
indigo, all that remains to be done is now to transform indol into isatine. 
The Chemistry of Hair-dyes. — Mr. G. McDonald, writing to the American 
Journal of Pharmacy (May), on the subject of a brown hair-dye, gives some 
chemical hints of considerable practical interest. Mr. McDonald says, the 
well-known fact that a soluble compound of lead and sulphur could not be 
obtained by the decomposition of a soluble lead salt by a soluble sulphuret, 
or, in other words, the insolubility of the sulphuret of lead was regarded as 
an indubitable proof of the folly of undertaking to search for a compound 
containing sulphuret of lead in a soluble state, and yet so as to be innocuous 
to the system. There is a class of salts known as hyposulphites, many of 
which are freely soluble in water, and which are readily converted by 
absorption of oxygen into sulphate of the base and free sulphur ; it is in the 
use of these salts that the key to the enigma lies. Chemical text-books 
state that hyposulphite of lead is insoluble in water, which is quite correct ; 
but, like many other precipitates insoluble in water, it is readily dissolved 
by an excess of the precipitant; thus, if we add to a solution of three parts 
of acetate of lead two parts of hyposulphite of soda, we shall have a curdy 
white precipitate of hyposulphite of lead, insoluble in water; but if we add 
to this ten parts more of hyposulphite of soda, the precipitate will be re- 
dissolved, and a perfectly clear solution will be the result ; this solution, 
when* applied to the hair, is decomposed by absorption of oxygen ; one of 
the results thereof is the formation of the dark brown sulphuret of lead ; it 
is to the formation of this compound in the hair that all lead and sulphur 
dyes owe their efficacy. 
