54 now cnopt4 pkEd, 



(3) b J giving rise to the funnivfion oi white famea, wllcri nny object (c. ^.^ 

 a glass rod) moistened witli hydrochloric iicid, is brouglit in contact with 

 it. These fumes arise Irom the formation of solid ammoniucAl salts pro- 

 duced by the contact of the gases. 



6. Xensler's Text.—Yov the detection of e.vceedin-ly minute liuccs of 

 ammonia, a reaction first pointed out by Nessler may be employed. Di- 

 gest at a gentle heat 2 grammes of iodide of potassium, and 3 grammes 

 of iodide of mercury, in 5 cub. cent, of water; add 20 cub. cent, of wa- 

 ter, let tlie mixture stand lor some time, then filter; add to the filtrate 

 30 cub. cent, of pure concentrated solution of i)otassa(l : 4); and, should 

 a precipitate form, filter again. If to this solution is added, in smnll 

 quantity, a liquid containing ammonia or an ammonia-salt, a reddisli brown 

 precipitate, or with exceedingly small quantities of ammonia, a yellow 

 coloration is produced from the formation of dimercurammouic iodide, 

 NHg2 I.OHj. 



c. Bohliff's Test. — According to Bohlig, chh^ride of mercury (corrosive 

 sublimate) is the most sensitive reagent for ammonia, when in the free 

 6t;ite or as carbonate. It gives a white precipitate, or in very dilute so- 

 lutions (even when containing but '|aoo,ooo of ammonia) a white turbidity, 

 due to the separation of niercurammonie chloride, NH^ Ilg.Cl. In solu- 

 tions of the salts of ammonia with other acids than carbonic, a clear 

 solution of mixed carbonate of potassa and chloride of mercury must be 

 employed, which is prcpaied by adding 10 drops of a solution of the 

 purest carbonate of potassa, (1 of salt to 50 of water,) and 5 drops of a 

 Bulution of chloride of mercury to 80 c. c. of water exempt from am- 

 monia (such is the water of many springs, but ordinary distilled water 

 rarely). This reagent may be kept in closed vessels for a time without 

 change. It much more concentrated, oxide of mercury separates from it. 

 Bj' its use the ammonia salt is first converted into carbonate by double 

 decomposition with the carbonate of potassa, and the further reaction 

 proceeds as before mentioned. 



Occurrence of Ainnionia in the Atmosphere. — The e.\- 

 istence of ammonia in the atmosphere was first noticed by 

 De Saussure, and has been proved repeatedly by direct 

 experiment. That the quantity is exceedingly minute has 

 been equally well established. 



Owing partly to the variable extent to whicli ammonia 

 occurs in the atmosphere, but chiefly to the difficulty of 

 collecting and estimating such small amounts, the state- 

 ments of those who have experimented upon this subject 

 are devoid of agreement. 



We present here a tabulated view of the most trust- 

 worthy results hitherto published: 



