66 BULLETIN OF THE NEW YORK STATE MUSEUM 



kettle or pan block to lie idle for a year, almost ruins it, 

 hence it is often cheaper to make salt for a season without 

 profit, than to leave the works to themselves. 



The main difficulty with which the salt manufacturers of 

 our state have to contend is the calcium sulphate or, as it is 

 called by them, and very properly, the plaster. In fact it 

 is this impurity, as I stated previously, which causes the in- 

 terruption of the process and the laborious cleaning out, 

 whether we use the kettle, the pan, the grainer or the 

 vacuum pan. It not only entails a great loss of heat in 

 consequence of its low conductivity, but it also causes the 

 overheating of the metal exposed to direct fire wherever this 

 is employed. While this is of little consequence in regard 

 to kettles, it is of great importance in regard to salt pans, 

 since their bottoms have usually only a thickness of \ to f 

 inches, and wherever they become coated with this plaster, 

 especially above and near the fires, overheating and unequal 

 expansion of the iron results they warp and become uneven. 

 It can easily be understood, that a proper removal of the salt 

 from an uneven pan bottom is very difficult and where the 

 warping is bad it is impossible. In consequence the salt 

 bakes on, is of inferior color, and the pan becomes leaky and 

 has to be repaired, which involves often not only heavy ex- 

 pense but loss of time. The heating of the brine as much 

 as possible in the back pan and the raising of its tempera- 

 ture near to the boiling point, in the second section of the 

 front pan before passing it into the front section are of 

 great service in the removal of all the calcium sulphate that 

 can be removed under ordinary circumstances. 



Suggestions and experiments have been made to over- 

 come this difficulty, involving the expenditure of great sums 

 of money, but without any practical results as far as me- 

 chanical means are concerned. 



The chemical means proposed, especially the use of 

 sodium carbonate and trisodium phosphate for the removal 

 of the calcium sulphate from the brine, would involve not 



