PURPOSE: To obtain a representative sample of refrigerant by metering a two phase refrigerant specimen containing a contaminant being introduced from a low pressure refrigerator into an expansible bag.

CONSTITUTION: A shutoff valve 37 and a purge valve 21 are opened to introduced a two phase refrigerant mixture from a refrigerator into a expansible tetra-bag 26. The mixture sealed hermetically in the bag 26 is equilibrated with the ambient temperature and the liquid phase refrigerant evaporates to fill the bag 26 with a uniform gas. A representative quantity of contaminant is thereby distributed uniformly in the bag 26 and accurate information of moisture or acid contained in the refrigerator in a refrigerator 10 can be obtained by passing the representative refrigerant specimen from the bag 26 through a test tube 50. When the refrigerant is equilibrated in the bag 26, a small quantity of representative refrigerant specimen is sucked into the test tube 50. If moisture is present in the specimen, it is absorbed in a moisture indicating section 62 to cause a change of color from blue to pink and the moisture is measured on graduations 76. In an acid is present, color is changed from blue to yellow at an acid indicating section 68 and the quantity is indicated.