10 
Prehistoric age — the Neolithic of the cave — is so great and 
so full of difficulty that it cannot be gauged by any method 
which has hitherto been invented. 
Mr. Boyd Dawkins also exhibited a remarkably perfect 
javelin head of bronze which had been dug up in a field 
near Settle. 
“Note on the Chromium Oxychloride described by Hr. 
Zettnow in Poggendorff’s Annalen der Physik und Chemie, 
No. 0, 1871,” by T. E. Thorpe, F.R.S.E. 
In the above-mentioned number of Poggendorff’s Annalen* 
Hr. Emil Zettnow describes an oxychloride of Chromium to 
which he assigns the formula Cr,Cl 4 0 + 4Cr0 3 . It is obtained 
by treating potassium chloro- chromate (K 2 Cr 2 0 6 Cl 2 ) with 
strong sulphuric acid, and, after a somewhat tedious course 
of preparation, appeal's as a brownish black, brittle, amor- 
phous substance, exceedingly hygroscopic, and giving up its 
chlorine with great ease. Hr. Zettnow’s analytical results 
and the numbers required by his formula are : — 
Found. 
Calculated 
Cr 
47 '28 
47-23 
Cl 
22-31 
21-42 
0 
31-35 
100.00 
In the Proceedings of the Literary and Philosophical 
Society of Manchester for Nov. 2nd, 1869,’f* I described a 
solid chromium oxychloride obtained by simply heating 
chromyl dichloride in a sealed tube, and which, on com- 
pletely freeing it from the latter body, “ appears as a black 
non-crystalline powder, which, when exposed to the air, 
rapidly deliquesces to a dark reddish brown syrupy liquid, 
which smells of free chlorine” (loc. cit.) These properties, it 
will be observed, are precisely those which Hr. Zettnow 
describes as belonging to his chromate of chrom-oxy chloride. 
* Sec also “ Cliem. News,” Sept. 15tli, 1871. 
t Also “Chem. News,” Nov. 19th, 1869. Zeitaelirift fiir Chemie, 
Jan., 1870. 95. 
