154 Scientific Intelligence. . 



mm. diameter. The ammonia was determined by means of a 

 normal hydrochloric acid, standardized by analysis and by pure 

 sodium carbonate. For titering back, one-third normal ammonia 

 solution was used, controlled by oxalic acid. Fluorescein was 

 employed as an indicator, since it can be used in daylight and 

 with artificial light as well. The results of the mixture used in 

 four different proportions, are given. In A, equal parts soda- 

 lime, sodium thiosulphate and sodium formate were employed. 

 In B, two parts soda-lime, one part sodium formate and 10 per 

 cent of sulphur. In C, equal parts soda-lime and formate, with 

 ten per cent sulphur. And in D, two parts thiosulphate, mixed 

 with one part of soda-lime and sodium formate mixed. The 

 latter mixture is preferred by the author who suggests the fol- 

 lowing points to be observed : (l) A canal in the mass in the 

 front of the tube should be avoided. In filling the tube, the 

 finely pulverized mixture containing the substance is first intro- 

 duced, the tube held vertically and jarred to compact the mass. 

 Then a mixture (either A or D) is placed in it, and then coarsely 

 pulverized soda-lime. (2) The mass in front must have a definite 

 length. In the analyses given this length was 15 cm., but 20 cm. 

 would be better. (3) The combustion in a 45 cm. tube requires 

 about one hour, a bubble of gas per second passing through the 

 receiver. (4) The process is a failure if the acid becomes turbid 

 or acquires more than a yellow color. (5) Not more than 0*5 

 gram, or, if the substance contains over 20 per cent nitrogen, not 

 more than 0*3 gram is to be used. (6) The mixture containing 

 the substance should occupy 12 to 15 cm., the mass in front of 

 this 15 to 20 cm. and the soda-lime 5 to 10 cm. of the tube. By 

 this method potassium nitrate gave 13-85, 13*77 per cent N, in- 

 stead of 13-86 ; sodium nitroprusside 28-20 and 28'15, instead of 

 28-13; trinitromethyl-toluidine 21-90, cal. 21*87; ethyl nitrocin- 

 namate 6-01, cal. 6-33; nitrosalicylic acid 7*56, cal. 7 - 65; strych- 

 nine nitrate, 10-60, cal. 10-60; morphine 4-50, cal. 4*62; m-hitro- 

 cinnamic aldehyde 7*89, cal. 7*91. — Ber. Berl. Chem. Ges., xviii, 

 806, April, 1885. G. F. B. 



2. On a new method of determining the Heat of combustion of 

 Carbon and of Organic compounds. — Two difficulties attend the 

 determination of the heat of combustion of carbon and its com- 

 pounds: one arises from the length of time required, the other 

 from the incompleteness of the oxidation. Berthelot and 

 Vieille have obviated these difficulties by effecting the combus- 

 tion in oxygen compressed to about seven atmospheres, in a 

 calorimetric bomb ; using a weight of combustible such that the 

 oxygen consumed by it does not exceed 30 to 40 per cent of the 

 whole quantity. The ignition is accomplished by a platinum 

 wire heated to redness by electricity and is completed in a few 

 seconds, sometimes with the characteristic noise given by an ex- 

 plosion in a closed vessel. The entire operation does not require 

 more than three or four minutes and is applicable to all sub- 

 stances whose vapor tension at the ordinary temperature is incon- 



