Is this Boiling point apparatus?
To me this looks like an apparatus to measure water in fat, butter or oil. A weighed sample of butter is placed in the conical flask. The tube A goes below the level of the melted butter or oil. It's purpose is to maintain atmospheric pressure or in case of a bump in the comical flask or back pressure or suction from the boiling tube D or the condensation flask C. Flask C should have a hole open to the atmosphere through the bung. The hole at the bottom of C is to remove water from the condensed ice. The conical flask is heated. The butter (oil) has a much higher boiling point than the water in it. So the water boils out. The tube from the conical flask will go well down into the boiling tube D. More than you have indicated in your diagram. Flask C should be full of an ice water salt mixture at −4 °C surrounding the boiling tube up to below the ventilation hole in D. It must not cover it or spill over into D as this would give you a wrong result. The thermometer measures the temperature in the region of D where the water condenses. If the thermometer indicates a rise in temperature above a set limit (I do not now have access to data where I could look up this temperature. However, I think it should be in the region of 5–10 °C) then the rate of heating show be reduced as you might overload the condenser and loose moisture. If the test has been running for some time it may be necessary to add ice as the ice melts to water the cooling efficiency of your condenser would be compromised. To do this some water should be run off from the tube at the bottom of flask C. This would be done Using the glass spout which you have shown. What you have not shown is the piece of rubber tubing (now long perished) and the clip attached to the spout at the bottom of C which would allow you to remove excess water from C. If you do not remove the excess water from C you could cause water to spill over into flask D as the ice is added from the top. If water were to get into D from C then your result would be destroyed and after cleaning everything out you would have to start over again. Remember it is necessary to have some water in C so that the ice can make better contact with D and act as a much more efficient condenser. The volume of water in the butter can be read on the side of flask D. It works well on low fat spreads which contain lots of water. If you want to use do not send for me. Good luck.