XXVIII] BAKING POWDERS 343 



G = the weight of the empty tubes; 



F = the weight of the fillings; 

 2.7 = the specific gravity of glass; 

 2.0 = the specific gravity of filling; 

 8.5 = the specific gravity of brass; 



G F 



— - + -— = volume of tubes and fillings; 



— -—— = volume of brass weights. 

 0.5 



9 RESIDUAL CARBON DIOXIDE— TENTATIVE. 



Weigh 2 grams of the baking powder into a flask suitable for the subsequent 

 determination of carbon dioxid, add 20 cc. of cold water and allow to stand 20 min- 

 utes. Place the flask in a metal drying cell surrounded by boiling water and heat, 

 with occasional shaking, for 20 minutes. 



To complete the reaction and drive off the last traces of gas from the semi-solid 

 mass, heat quickly to boiling and boil for a minute. Aspirate until the air in the 

 flask is thoroughly changed, and determine the residual carbon dioxid by absorption, 

 as directed under 5 or 8. 



The process described^ based on the methods of McGilH and Catlin^, imitates 

 as far as practicable the conditions encountered in baking but in such a manner that 

 concordant results may be readily obtained on the same sample and comparable 

 results on different samples. 



10 AVAILABLE CARBON DIOXID.— TENTATIVE. 

 Subtract the residual carbon dioxid from the total. 



1 1 ACIDITY.-TENTATIVE. 



(For cream of tartar and its substitutes.) 



Dissolve 1 gram of the sample in hot water and titrate with N/5 potassium hy- 

 droxid, using phenolphthalein as an indicator. 



TARTARIC ACID, FREE OR COMBINED. 



12 Wolff Method^— Tentative. 

 (Applicable in the presence of phosphates.) 



Shake repeatedly about 5 grams of the sample with about 250 cc. of cold water 

 in a flask and allow the insoluble portion to subside. Decant the solution through 

 a filter and evaporate the filtrate to dryness. Powder the residue, add a few drops 

 of 1% resorcin solution and about 3 cc. of strong sulphuric acid and heat slowly. 

 Tartaric acid is indicated by a rose-red color which is discharged on dilution with 

 water. 



TOTAL TARTARIC ACID. 



1 3 Goldenherg-Geromont-Heidenhain Method. — Tentative. 

 (Applicable only in the absence of aluminium salts, calcium salts and phosphates.) 



Into a shalloAV 6 inch porcelain dish weigh out 2 grams of the sample and suffi- 

 cient potassium carbonate to combine with all the tartaric acid not in the form of 

 potassium bitartrate. ' Mix thoroughly with 15 cc. of cold water and add 5 cc. of 

 99% acetic acid. Stir for 30 seconds with a glass rod bent near the end. Add 100 

 cc. of 95% alcohol, stir violently for 5 minutes, and allow to settle at least 30 min- 



