154 ILLINOIS ACADEMY OF SCIENCE 



the improvement obtained by the treatment. The curves for 

 the commercial grades of iron are far below. 



Turning now to the more recent results obtained with the 

 silicon alloys. Here it is seen that two maxima occur in the 

 curve for maximum permeability corresponding to two minima 

 in the curves for hysteresis loss and coercive force. The first 

 of these occurs with a silicon content of 0.15 per cent and the 

 second with a silicon content of 3.5 per cent. The electrical 

 resistance increases uniformly with the silicon content so that 

 an alloy containing 3.5 per cent silicon has a specific resistance 

 nearly five times that of pure iron. 



Fig. 4 gives a comparison between the 3.5 per cent silicon 

 vacuum-alloy and 4 per cent commercial silicon steel, both 

 tested by the Burrows method. It is seen that the maximum 

 permeability is as 20 to 1, the hysteresis loss for B max = 10000 

 as 8 to 1, and the hysteresis loss for B max = 15000 as 4 to 1 

 in favor of the vacuum product. 



Could this vacuum alloy be substituted for the present com- 

 mercial steel in transformers and used in a form to give the 

 same properties as shown in Fig. 4 it would be possible to 

 increase the flux density from B max = 10000 gausses to nearly 

 15000 without increasing the required magnetizing force and 

 at the same time to decrease the hysteresis loss to less than 

 one-third. Consequently the cross section of the iron core 

 for a certain flux could be decreased to two-thirds and the 

 length of the copper wire for the windings could be corre- 

 spondingly reduced. Thus besides a lowering of the hys- 

 teresis loss there would result also a lowering of copper 

 loss, and, with the eddy current loss only slightly increased, 

 the sum total should be a transformer of about two-thirds 

 the weight with an energy loss of about one-half that of a 

 similar transformer with an ordinary silicon steel core. 



It is well known, however, that the core of a transformer 

 must be made up of iron in the form of very thin sheets in 

 order to 'keep the eddy currents down to a proper value, 

 otherwise the loss caused by these eddy currents would be 

 excessive. Now, the properties of the vacuum alloy were 

 obtained with the alloy in the form of a rod 1 cm. 

 in diameter. Whether it is possible to duplicate them 



