oxygen and nitrogen in a double glazed window eliminates pressure variations within the window space created by such gas movement application_number US 90005278 A description molecular sieve zeolites now generally referred to in the art as type a molecular sieve zeolites are described in u s pat no 2 882 243 type a zeolites are described as truncated cube octahedrons having an internal central cavity or cage of 11 a u00b0 diameter the central cavities are entered through circular apertures of much smaller diameter the diameter being determined by the specific cations contained for instance the type 4 a molecular zeolite has the formula na 12 alo 2 12 sio 2 12 xh 2 o when fully hydrated x is 27 but the sieve is activated to give it adsorbent capability by heating to drive the water of crystallization off until the water content of the total composition is reduced to 1 5 by weight or below the type 4 a sieve has an aperture opening about 4 a in diameter when a substantial proportion of the sodium content of the 4 a sieve is replaced by potassium the aperture diameter is reduced to about 3 a for example the type 3 a molecular sieve is formed.