D. CHEMISTRY AND METALLURGY. 231 



to the autumnal equinox, and then diminishes; that the 

 quantity is not greater in rain which falls during a thunder 

 shower; and that during the four months the absolute 

 quantity of hydrogen peroxide contained in the 221 liters 

 of rain which fell upon each square meter was only 62.9 

 milligrammes. In snow there was only 0.05 milligramme 

 of peroxide to the liter, the amount diminishing toward the 

 winter solstice. Natural dew and frost contain no peroxide, 

 or at least less than one twenty-five millionth of this sub- 

 stance. In artificial dew and frost the amount of peroxide 

 varied from 0.04 to 0.06 milligramme per liter, reaching on 

 a bright moonlight night in summer 0.09 milligramme. The 

 amount increased with the altitude of the sun. The daily 

 maximum was reached between 12 and 4 o'clock P.M., and 

 the annual maximum in the month of August. The amount is 

 greater the higher the temperature, the clearer the sky, the 

 higher the absolute and the lower the relative humidity of the 

 air. The author concludes that the peroxide is contained in 

 the air both free and in solution, to the extent as a maximum 

 of 0.000000268 c. c. in a liter. He also believes that sunlight 

 plays an important part in its production. 35 C t VII., 1693. 



TARTRONIC ACID A GLYCERINE OXIDATION PRODUCT. 



Hitherto tartronic acid has only been known as a product 

 of the spontaneous decomposition of nitro-tartaric acid and 

 as a reduction product of mesoxalic acid. Theoretical con- 

 siderations led Professor Sadtler, of the University of Penn- 

 sylvania, to conceive that this acid might be formed by the 

 oxidation of glycerine, and hence to search for its presence 

 in the products of this reaction. For this purpose one part 

 * of glycerine was mixed with an equal weight of water, and 

 to this was added about one and a quarter parts of fuming 

 nitric acid. This latter was poured into the vessel through 

 a long funnel tube, so as to form a layer upon the bottom. 

 After about six days the evolution of gas had ceased, and 

 the solution was evaporated at a gentle heat to a sirupy 

 consistence, then diluted, and lead carbonate added in ex- 

 cess. The liquid filtered from the mixed lead oxalate and 

 carbonate gave, upon evaporation, thick crusts of lead glyc- 

 erate. These, redissolved in water, were freed from lead by 

 hydrogen sulphide, the solution concentrated, neutralized by 



