Polytechnic Association. 621 



green. It will take a good deal of white without showing it in the 

 yellow color ; but mixing blue with it detects it at once. 



Mr. Reuben Bull — The chromate of potash acts like prussiate in 

 hardening. The prussiate of potash leaves a scale upon the metal ; 

 the chromate leaves it cleaner ; but the cyanide of potassium leaves 

 it very clean. 



Dr. Yan der "Weyde — When you use the cyanide you make a 

 carbon steel ; but when you use the chromate of potash you make a 

 chrome steel. 



Mr. J. K. Fisher — The safe-makers are using chrome steel. Marvin 

 introduced chrome steel for that purpose. The strength of the chrome 

 steel has been estimated at 140,000 pounds. It will be recollected 

 that last season we had here a sample of the Sherman steel, stated to 

 sustain 263,000 pounds to the square inch of section. The Bessemer 

 steel comes up to about 130,000 pounds, but it is not uniform. I 

 would like to know whether the chrome steel is uniform, and whether 

 it is an expensive steel. 



Dr. Feuchtwanger — It is not more expensive than any other 

 steel. 



Prof. James A. Whitney — According to Osborn's recent work, 

 chromium steel is inferior for tool making to the best made crucible 

 steel of ordinary manufacture. But these kinds of steel are of little 

 consequence compared with low steel. The quantity of high steel 

 used in this country is small compared to the low steels that either 

 now find, or must hereafter find, application for rails, axles, steam- 

 boilers, etc., as a substitute for wrought iron. I may mention, inci- 

 dentally, that two or three years ago I saw steel cylinders, of steel 

 about one-sixteenth of an inch in thickness, which had been tested 

 with a pressure of 600 lbs. to the square inch ; and they were bulged 

 out in the center into a barrel shape, while cast steel cylinders of the 

 same size and thickness showed no change from the severe test. 



Dr. Feuchtwanger — The chrome steel is not so good as the tung- 

 sten steel ; but it can be made cheaply. Chromic ore can be bought 

 for $4 a ton. 



Dr. L. Bradley suggested the use of chromic acid instead of bichro- 

 mate of potash for batteries, as probably cheaper ; but, learning that 

 the former costs forty cents and the latter seventy -five cents, con- 

 cluded that there was no material difference in cost, taking into 

 consideration the work done by each 



Dr. Yan der Weyde stated that he had ascertained by experiments 

 that bichromate of potash and sulphuric acid would bleach linseed 



