1*atm1⋅atm will support a column of mercury 760760 mmmm high. You can use a mercury column to measure a reduced pressure, or you could use a mercury bubbler as a control to release excess gas, but you would always be aware of the possibility that if you break your glassware, or have some other accident, events which are all too possible in a laboratory, you will get mercury all over your bench, where the metal will inhabit every nook and cranny. This will be a major clean up job, which a contract cleaner would not touch.
So, to your problem, we have a starting pressure of,
"34200 mm Hg"/("760 mm Hg "atm^-1)34200 mm Hg760 mm Hg atm−1 == 45*atm45⋅atm, P_1P1.
And an end pressure of,
"1400 mm Hg"/("760 mm Hg "atm^-1)1400 mm Hg760 mm Hg atm−1 == 1.84*atm1.84⋅atm, P_2P2.
Using Charles' Law, (P_1)/T_1=(P_2)/T_2P1T1=P2T2
So T_1=(P_1)/(P_2)xxT_2T1=P1P2×T2 == (45*atm)/(1.84*atm)xx308*K45⋅atm1.84⋅atm×308⋅K, which is a rather high temperature.
I reiterate that the question is highly suspect, and the units are physically impossible.