86 Mr. EK. T. Harpman—On the Chemical Composition of Chert. 
ANALYSES OF THE SPECIMENS. 
No. 2. A dark chert, very hard but brittle ; cannot be scratched with a knife ; 
effervesces freely with acid. 
Anatysis IL 
Total 
C UY Analysis 
Silica (Si O,) (Insoluble), : ; = 79°82 79°82 
Silica (Si O,) Nea Re : : 1:00 - 1-00 
aa, 6 : _ 0:79 0:79 
A1,0,, 1:05 1:94 2:99 
FeO, 0:20 2:00 2:20 
*CaO 0°81 0°81 
MgO, - trace trace 
CaCO,, 12:00 — 12-00 
MgCoO,, trace - trace 
SrCO,, traces ~ os 
Fl, ” Te » 
Na,O, ” vi ” 
K,O, ” Th ” 
Water and organic matter, 0-20 ~ 0-20 
Insoluble residue, ‘ < : 85-43 = = 
99-81 85°36 99°81 
Specific gravity not determined. 
With Smithson’s modification of Berzelius’ method very appreciable traces ot 
Fluorine became apparent, but not enough to estimate. 
No. 8. Hard dark’chert, cannot be scratched ; but effervesces freely with acid. 
Anatysis II. 
Total 
2 Analysis 
Si0, (Insoluble), : - 80-45 80°45 
SiO, (Soluble), : . : trace - trace 
Fe,0,, : ! f 
ioe \ k ; 0-55 1-73 2-98 
FeO, ; 3 ‘ ‘ traces — trace 
Cao, : : ; = 0:53 0:53 
SrSO, - BaSO,, : i : 0:43 = 0:43 
CaCO, ; : 14-62 =~ 14-62 
MgCoO,, trace — trace 
Na,0, 0 ” TR ” 
Fl. very distinct traces, 3 - 5 
Water and organic miter 1:60 = 1:60 
Insoluble endae 82°75 _ = 
99-95 82:71 99-9] 
Specific gravity, 2°625.+ 
In this specimen also there are distinct traces of Fluorine, confirming Professor 
Hull’s determinations of fluor-spar. Strontium and Barium are also present, doubtless 
combined with the small portion of sulphuric acid also observed as above. It has 
occurred to me that the hexagonal forms which Mr. Hull has noticed (ante), may 
* The lime and magnesia found in the insoluble residue in this and other specimens, are doubtless 
combined as silicates. 
t The specific gravity of most of these specimens was kindly determined for me by Mr. W. Plunkett. 
F.C.S., Royal College of Science, Dublin. 
