OXALIC ACID AND URANIUM SALTS AS A PHOTOMETER. 301 



many cities in the temperate zone tends to a certain extent to equalize 

 the lower intensity as compared to Manila. 



Some general comparisons of the action of sunlight in Chicago and 

 Manila are brought out in the following table, 100 cubic centimeters 

 of solution containing 5 grams oxalic acid and 1 gram uranyl acetate in 

 a 100 cubic centimeters Erlenmeyer flask, being used in ever}' case : 



Chicago, May-June, 1910. 



Time. ' 



Minutes. 



Cubic 

 centime- 

 ters of 

 gas. 



12.20 p. m. to 3. 05 p. m 



12. 51 p. m. to 2. 51 p. m 



10a. m. to 12. lop. m 



9. 25 a. m. to 10. 55 a. m 



11 a. m. to 12.20 p. m 



165 



120 



135 



90 



80 



60 



150 



120 



90 



60 



77 

 55 

 85 

 51 

 58 

 15 

 43 

 62 

 58 

 36 



9.35 a. m. to 10.35 a. m 



9 a. m. to 11. 30 a. m 



11.30 a. m. to 1.30 p. m 



1.30 p. m. to 3 p. m 



3 p. m. to 4 p. rrj __ 



Total 



1,070 



540 





These figures show that, in the series carried on in Chicago, approxi- 

 mately 100 cubic centimeters of gas were evolved in two hundred minutes. 



Manila, October-November, 1909. 



Time. 



Minutes. 



Cubic 

 centime- 

 ters of 

 gas. 



10. 45 a. m. to 12 m. _ _ 



9.25 a. m. to 10.20 a. m 



10.25 a. m. to 11. 10 a. m _ 

 1 11.25 a. m. to 12 m. .. _ 



10.40 a. m. to 11.20 a. m 



1 p. m. to 1.40 p. m 



9. 40 a. m. to 10. 15 a. m 



11.25 a. m. to 12 m 



9.35 a. m. to 10.10 a. m 



85 



-- 



00 



45 

 35 

 40 

 40 

 35 

 35 

 35 



214 



153 



143 



81 



84 



78 



82 



80 



103 



Total 



405 | 1,018 



. Therefore, in the series carried on here, 100 cubic centimeters of gas 

 were evolved in forty minutes, or the rate was approximately five times 

 that of Chicago. Many more measurements will now be made in tem- 

 perate zones and in Manila before we conclude absolutely that the actinic 

 power of the sun in carrying on this reaction is so much greater in the 

 Tropics -than in more northern latitudes. 



