WAEMING AND VENTILATING OCCUPIED BUILDINGS. 



309 



Y the volume which it occupies at the temperature to ; and 

 «=0.002036=a constant co-efficient obtained by exj)eriment, and 

 which expresses the proportion in which the volume increases for 

 each degree Fahrenheit. 

 This formula shows that, under the same barometric pressure, a vol- 

 ume of one cubic foot of air at 32^' becomes — 



[l-\-a {t—S2) ]=[ 1+0.002030 it—32)] cubic feet in passing to the 

 temperature of t degrees. 

 If the temperature falls instead of rising, the air contracts, its volume 

 diminishes in cooling, and it follows in this contraction the same law, 

 expressed by the formula — 



V=[l-. 002036 (i-32)] Vo=f 1-a (^-32)] Vq 

 which is the same as the preceding formula, if the temperature t is con- 

 sidered plus when above and minus when below. 



32. Variation of density. — When the temperature of the air rises and 

 its volume increases, its density, or the weight of a cubic foot, diminishes 

 according to a law expressed by the following formula, assuming that 

 the atmospheric j)ressure remains constantly equal to that of 30 inches 

 of mercury : 



d= <^o _ 0.081 



— l + a{t-32) ~ 1+0.002036(^-32) 



The density or the weight of 1,000 cubic feet of air at different tem- 

 peratures, calculated by the above formula, is given in the following 

 table : 



Temperature by 

 Fabreubeit's 

 tbermometer. 



o 

 o 



Temperature by 

 Fabreubeit's 

 tbermometer. 



o 

 o 



Temperature by 

 Fabreubeit's 

 tbermoraeter. 



o 

 o 

 o 



"S.2 



Temperature by 

 F a b r e ubeit's 

 tbermometer. 



o 

 o 



o 



IB o 



c 



Lbs. 



o 



Lbs. 



o 



Lbs. 



o 



Lbs. 



—4.0 



.0875 



64.4 



.0760 



132.8 



.0673 



201.2 



. 0603 



—0.4 



.0868 



68.0 



.0755 



136.4 



.0669 



204.8 



.0600 



3.2 



.0861 



71.6 



.0751 



140.0 



.0665 



208.4 



.0597 



6.8 



.0855 



75.2 



.0748 



143.6 



.0661 



212. 



.0594 



10.4 



.0849 



78.8 



.0741 



147.2 



.0657 



215.6 



,0591 



14.0 



. 0842 



82.4 



.0736 



150.8 



.0653 



219.2 



.0587 



17.6 



.08.36 



86.0 



.0731 



154.4 



.0649 



222. 8 



.0584 



2L2 



. 0829 



89.6 



.0726 



158.0 



.0646 



226. 4 



,0581 



24.8 



.0824 



93.2 



.0721 



161. 6 



.0642 



230. 



.0578 



28.4 



.0819 



96.8 



.0716 



165. 2 



.0638 



233. 6 



. 0575 



32. 



.0811 



100.4 



.0712 



168.8 



.0634 



237.2 



.0572 



35.6 



.0803 



104.0 



.0708 



172.4 



. 0631 



240.8 



.0569 



39.2 



.0799 



107.6 



.0703 



176.0 



. 0628 



244. 4 



. 0566 



42.8 



.0794 



111.2 



. 0699 



179.6 



.0624 



248.0 



.0563 



46,4 



. 0788 



114.8 



.0694 



183. 2 



. 0620 



251. 6 



.0561 



50.0 



.0783 



118.4 



.0690 



186.8 



.0616 



255. 2 



. 0558 



53.6 



.0777 



122. 



.0686 



190. 4 



.0613 



258.8 



. 0555 



57.2 



.0771 



125. 6 



. 0681 



194.0 



.0610 



262.4 



.0552 



60.8 



.0766 



129.2 



.0677 



197.6 



.0606 



266.0 



> .0549 



