Cclxxxiv GENERAL SUMMARY OF SCIENTIFIC AND 



constituents of a gaseous mixture, converting each into a 

 solid or liquid form, in which condition they can be weighed 

 on a balance. Professor Wurtz alludes in his memoir to 

 the fact that gravimetric methods for gas analysis were suc- 

 cessfully employed by chemists some thirty years ago, and 

 expresses his surprise that so little has been done to de- 

 velop their capabilities. The general outline of his method 

 is about as follows : In a crude coal gas, as drawn from the 

 hydraulic main, the gas-chemist should be able to separate 

 and determine with precision the following : (l) Tar, sus- 

 pended in the form of spray ; (2) Water, do. ; (3) Water, as 

 vapor, dissolved in the gas ; (4) Naphthaline (condensible) ; 

 (5) Other condensible hydrocarbons ; (6) Smoke and soot 

 (with dust) ; (1) Ammonia ; (8) Carbonic acid ; (9) Sul- 

 phureted hydrogen ; (10) Carbonic oxide ; (11) Oxygen 

 (intermixed air). 



Of these eleven proximate constituents, Professor Wurtz 

 affirms that he has succeeded in separating with very satis- 

 factory sharpness Nos. 1, 2, 3, 6, 7, 8, 9, and 11, eight in 

 all, besides approximating to No. 4 the naphthaline in ex- 

 cess. Nos. 5 and 10 are still subjects of experiment. The 

 following are the devices and manipulations employed : 

 First. Arresting suspended matter by means of empty dry 

 flasks, and straining through cotton previously desiccated. 

 Absorbing next the ammonia, by means of re-agents which 

 act on no other ingredient. Next, drying the gas with 

 calcium chloride, which, ammonia being absent, may now 

 be done. Next, taking up the sulphureted hydrogen by 

 a normal metallic salt, so selected or so managed as to 

 give up no water or acid vapor to the desiccated gas. 

 Next, using sodic hydrate to absorb the carbonic acid, with 

 certain jn-ecautions. Next, alkalized pyrogallol, or other 

 suitable agent, to absorb oxygen, arranged so as to lose no 

 water. The final (rough) measurement of the gas is then 

 made at an observed temperature by a gas-meter. The 

 whole process is finally completed by a process of distilla- 

 tion, either at the ordinary or higher temperature in a cur- 

 rent of the same gas analyzed, that has been subjected to 

 similar treatment, and thus freed from all the ingredients to 

 be separated from each other. After final weighings, the 

 correct initial volume of the gaseous mixture is calculated 



