146 Scientific Intelligence. 
over a Bunsen burner gave a strong reaction, The importance of 
this result, with reference to the determination of nitrites in, natu- 
ral waters, led to an investigation of the cause of, oe result, First 
it appeared that a liter of distilled water evaporated in a retort, 
either exhausted or at atmospheric proaeures ie no reaction for 
nitrous acid, and hence proved the air to be the source of the con- 
tamination. Another liter with 5cc. oe water, was evaporated in 
a glass basin 64 inches in diameter over a Bunsen rose burner. The 
reaction given was strong and corresponded to about 0°05 mgrm, of 
nitrogen. Since a second similar ev aporation conducted with 
steam gave only 0°004 mgrm. nitrogen, it was clear that the 
nitrous acid had mainly come from the combustion of the gas used 
as fuel. But still even in the residue obtained with steam, the 
eee appeared, That this came directly from the air of the 
ro shown by placing a second basin of airs water by 
the ee of the first during the evaporation. After twenty-four 
hours a full rose tint was developed; and this without any senst- 
ble evaporation. For extremely accurate work, water then must 
be evaporated in close vessels; but for ordinary purposes, the con- 
centration may be effected in a steam bath. 
Warington gives in his paper some experiments made with the 
one es of a wteke ditaraeed soticion of ‘al i nilic acid pes one 
drop of a saturated solution of naphth ylamine ld a an The 
standard solution was made with potassium nitrite prepared from 
ure silver nitrite. With a solution of 1 part of nitrogen as nitrous 
acid in 1,000,000 parts of water an immediate pink color appeare 
which rapidly became deep ruby red; in 10,000,000 parts, at once 
a pink, and at the end of an hour a full site in 100,000,000 parts 
a pink tinge in six minutes and a pal e pink in an ‘hour; Sade 
500,000,000 parts (lec. of the millionth seean in a half liter of 
hours, and a distinet pink color in twenty-four hours. In the last 
two experiments similar flasks to which no nitrite had been added 
were similarly treated, but without result, During the reading © 
the paper in the Chemical Society’s room, the presence of nitrous 
acid in the air was shown by exposing 20000. of water containing 
the test, to the atmosphere there in a basin for four 
pouring it into a cylinder, it had become rose-pink as was seen on 
comparing it with a similar cylinder which had been closed with a 
