“…In conijunction with X-ray diffraction techniques which determine similar properties within the core -of the particle, it may provide much useful information concerning the relation between the physical structure of dust and its physiological effects. At (32), which has proved saltisfactory for sampling aimmonia, nitrogeen oxides, aldelyvdes and sulfur dioxide, freeze-out trains, largecapacity plastic bags, silica grel, and other solid absorbents (33).…”