160 Ozone and Ozone Tests. 



only in a saturated solution. He observed that certain metallic 

 chlorides, particularly chloride of copper and sesqui- chloride of 

 iron, give coloured images still more readily than a mere 

 solution of chlorine. Portraits artificially but skilfully coloured 

 have been sold as the pure products of heliochromy; no coloured 

 photograph has, however, as yet been produced by it. 



Photography has already become of the highest importance, 

 its votaries are scattered in tens of thousands over every part of 

 the world ; it has been pressed into the service of every art, 

 science, and manufacture. Nor are its uses confined to the 

 requirements of tranquillity and peace ; it has been made a 

 portion of the appliances of war, and on a rather considerable 

 scale, as appears from a paper read before the Photographic 

 Society of London, in December last.* The extent to which 

 it has caused an increase in the consumption of chemical sub- 

 stances may be conceived from the fact that, at Frankfort, ^ 

 during the year 1862, 5400 German pounds of the finest grain 

 silver, worth 163,428 thalers (about £36,000), were devoted to the 

 manufacture of nitrate of silver alone [Photographisches Archiv. 

 Sep. 1863]. 



OZONE AND OZONE TESTS. 



BY E. J. LOWE, F.K.A.S., E.G.S., ETC. 



Ozone is a subject that has attracted a large amount of interest 

 within the last few years. Schonbein, in making the important 

 discovery of ozone in the atmosphere, added fresh work to all 

 meteorological observers, and their labours have thrown some 

 light on the subject. To those who have no knowledge of this 

 new property of the air, it may be said that, if a piece of paper 

 be (lipped into, or coated over, with a, solution consisting of 

 starch, iodide of potassium, and distilled water, dried and then 

 exposed to the air, it becomes more or less coloured, according 

 to the amount of ozone present at the time. Dr. Moffatt, who 

 was tlie first to take up this subject in England, has rendered 



'_•■ t ■ f ■ .- 1 1 service to science, ami his tests have been almost univer- 

 sally adopted by English meteorologists for a number of years; 

 and although an extended series of experiments has convinced 

 in" thai the tests I am mm- making are purer, and better 

 adapted for a thorough insight into this chemical property of 

 the ■■i'w, nevertheless ourwarmest thanks are due to Dr. Moffatt 

 for his valuable labours in this branch of science. Before turn- 

 ing to ozone tests, we will say a, few words on ozone itself. 



* Photographic Journal, Dec. 18G3. 



