TRANSACTIONS OF WAGNER 



THE CHEMISTRY OF BREAD-MAKING 



When cream of tartar (potassium acid tartrate) is used : 



KHC4H4O6 + NaHCOa -^ CO2 + H2O + KNaC4H406 



Potassium 

 acid tartrate 



Sodium 

 acid carbonate 



Carbon 

 dioxid 



Water 



Potassium 

 sodium tartrate 



The residue in the first case is sodium tartrate and in the second potassium 

 and sodium tartrate, better known as Rochelle salt or Seignette salt. Both 

 of these salts are purgative in their action and remain in the bread or biscuit 

 as substances not normally in the human body nor of any especial use to it. 

 The amount of Rochelle salt left in food made with a cream of tartar baking- 

 powder is almost exactly equivalent in weight to the amount of baking-powder 

 originally used, as the Rochelle salt crystallizes with four molecules of water 

 of crystallization, which largely increases its weight. 



In the phosphate baking-powders the reactions are as follows : 



When acid calcium phosphate is used : 



CaH4(P04)2 + 2NaHC03 



Calcium acid Sodium acid 



phosphate carbonate 



dioxid 



When acid sodium phosphate is used : 



NaH2P04 + NaHCOs -^ CO2 



Sodium acid 



phosphate 

 (monosodium 



phosphate) 



CO2 + H2O -1- Na2HP04 -I- CaHP04 



Carbon Water Disodium Monocalcium 

 phosphate 



+ 



Sodium acid 

 carbonate 



Carbon 

 dioxid 



H2O 



Water 



+ 



phosphate 



Na2HP04 



Disodium 

 phosphate 



The residue in the first case is a mixture of disodium phosphate and mono- 

 calcium phosphate. The monocalcium phosphate is an insoluble salt which 

 passes through the aUmentary tract mostly unchanged. The disodium phos- 

 phate, which is the sole fixed residue of the second reaction, and is also present 

 in the first reaction, is the soluble salt commonly known and used as a cathartic 

 under the name of sodium phosphate. The amount of this salt is only a little 

 more than half of the original weight of baking-powder taken. 

 In the alum powders the reactions are as follows : 



K2Al2(S04)4 + 6NaHC03 - 



Potassium Sodium acid 



aluminum carbonate 

 sulfate 



(NH4)2Al2(S04)4 + 6NaHC03 



Ammonium Sodium 



aluminum acid 



sulfate carbonate 



> 6CO2 + K2SO4 + 3Na2S04 + 2A1(0H)3 

 Carbon Potassium Sodium Aluminum 



dioxid sulfate sulfate hydroxid 



^ 6CO2 + (NH4)2S04 + 3Na2S04 + 2A1(0H)3 



Carbon Ammonium Sodium Aluminum 



dioxid sulfate sulfate hydroxid 



Na2Al2(S04)4 + 

 Sodium 

 aluminum 

 sulfate 



6NaHC03 



Sodium acid 

 carbonate 



6CO2 



Carbon 

 dioxid 



+ 



4Na2S04 

 Sodium 

 sulfate 



+ 



2A1(0H)3 



Aluminum 

 hydroxid 



