Development of Karl Fischer Reagents

III-1. Industrial Products
4. Liquefied Petroleum Gases
Liquefied petroleum gases, such as propane and butane, can be
added directly to dehydrated solvents or electrolytes and subjected to
Karl Fischer titration, using either the volumetric or coulometric
methods. Coulometric titration is most suitable, since liquefied
petroleum gases usually contain only trace amounts of moisture.
To obtain accurate measurements of moisture content, it is important to
add the sample in the liquid phase. In particular, allowance must be
made for a marked tendency for fluctuations in the moisture content of
samples at around the 50ppm level. Be sure to inject the entire sample
into the sampling bottle. For details of the methods used,
refer to the LPG Testing Method Standards of the Japan LPG
Association.
138
Key Points
Reference:Muroi, K. et al., "Rapid Determination of Water in LPG by
KarlFischer Method" J. Japan Petroleum Institute 11, 440
(1968).
Sampling Method
Liquid-phase samples are obtained as follows.
(1) Place the canister containing the gas upside-down or on an angle.
Connect a high-pressure sampling bottle to the canister outlet using a
hose designed for this purpose (Figure 22).
(2) Open valves A and B of the sampling bottle. Next, gradually open the
valve on the canister, allowing a small amount of the gas to vaporize.
Release the gas through the sampling bottle.
(3) Close valve B, and open the valve on the canister to release the sample
into the sampling bottle.
Note:The sample can be moved into the sampling bottle by opening
and closing valve B, repeatedly. Do not fill the bottle completely
with liquid sample. Always keep the sample below 80% of the
volume and leave some vapor space.