120 Scientific Proceedings, Royal Dublin Society. 
scarcely due to Pettenkofer, but yet his name has become so 
inseparably connected with it that no matter what modifications 
may have been introduced as regards the form of collecting vessel, 
the method of filling it with air, the nature and strength both of ~ 
absorbing solution and standard acid, and the kind of colour 
indicator used, the process may still be properly spoken of as 
“< Pettenkofer’s.”’ 
Almost at the outset of our experiments a possible source of 
error suggested itself which it is true had been touched on by 
others, but did not appear to us to have been sufficiently investi- 
gated, viz. the action of the alkaline absorbent on the glass 
surface of the receiving vessel. 
Preliminary experiments showed that very dilute baryta water 
exercised an appreciable action on glass, silica being dissolved and 
the titre of the solution affected. 
Having satisfied ourselves on this point, it occrred to us that 
this source of error might be entirely avoided by coating the inner 
surface of the receiving vessels with a layer of some substance 
which the baryta could not act upon. Paraffin wax suggested itself 
as suitable for the purpose; and with receivers coated with that 
substance we at once obtained fairly satisfactory (¢.e. concordant) 
results, as the following table shows :— 
Sreries 1.—(Azr.) 
Determinations performed in paraftined bottles—which were also 
used as titrating vessels. 
No. of | Baryta nasal Carbonic | Capacity PEO Dur fe 
‘ment. | added, | Feauired. | maytate | Oy, | founds" | from | absorption, 
icine, || HASas 
1 | 70 c.c. | 63°6c¢.c. | 0°64 ¢.c. | 2570 c.c. | 2°49 | — 0-03 | about 24 hrs. 
DV og op | CBOs | OFS 5, | DLS o, || Sai | = Ol ie 
3 | ODS eee Oae) 4, || 2520 |) Bel | OOD |) 2 iowa. 
|| og op I CRM aI (HES. || 2568 5, || MA | = O08 fr 
3 |p mp CERO I eRe | 570 45 | BRD | |] SS OHOR |) 119 nares. 
B® oop op 1) SRO 5 OO a5 | BBB 55 |) BBR |e OPN a 
Mean =| 2°52 
