Edward Y. H. Keng invented an instrument which he named it "helium pycnometer" in 1967. The first U.S. Patent on this invention was issued in 1969. Another U.S. Patent on this instrument was issued in 1971.
Edward Y. H. Keng (耿蘊和),“Air and Helium Pycnometer”
Published in Powder Technology, Vol.3, No.3, P.179-180, 1969
(This article is presented in the Supporting Information)
Edward Yun Ho Keng has two U.S. Patents on helium pycnometer:
“Method and Apparatus for Volume Measurement”
U.S. Patent No. 3,453,881 (1969)
“Method for Measurement”
U.S. Patent No. 3,585,861 (1971)
WHAT IS A HELIUM PYCNOMETER?
The helium pycnometer is a scientific instrument that allows measuring the volume and true density of solid objects, without damaging samples. This is accomplished by employing Arch imides' principle of fluid displacement and Boyle's law to determine the true volume of a sample. The displaced fluid is helium which can penetrate the finest pores, thereby assuring maximum accuracy.
The unique nature of the helium pycnometer is that it allows determining the actual density of a sample without taking into account the volume occupied by internal or open porosity. The principle of this method is based on putting a sample of known mass into a cell of known volume. Then helium is introduced into the cell which is at a vacuum, so helium occupies the entire volume of the cell that is not occupied by the sample. The actual volume of the sample can be determined since the volume of cell is known. The actual density of the sample material then can be accurately determined by this technique.
“ Air and Helium Pycnometer,” Powder Technology, 3 , No. 3, 179-180, 1969.
Air and Helium Pycnometer
Abstract: The volume and density of powders and porous and irregularly shaped solids can be obtained rapidly and accurately by means of a newly designed gaseous pycnometer. The pycnometer has been successfully used with either air or helium. Air is employed for inert low-surface materials on which negligible adsorption of gas occurs. For fine powders or porous materials, helium, an inert gas, is recommended if a precise measurement is to be attained. Helium must be used with activated samples or those having a high surface area.
Helium Pycnometry has been used to measure the density of many different samples so accurately that it is considered as the most important method since it was invented by Edward Y. H. Keng forty years ago at Georgia Tech.
Title:METHOD AND APPARATUS FOR VOLUME MEASUREMENT United States Patent 3453881
United States Patent 3585861
METHOD FOR VOLUME MEASUREMENT