Allen — The Insulating Properties of Erinoid. 



333 



The larger percentage gain in weight for a shorter period of immersion 

 than in the preceding test, is due to the surface-area being nearly double of 

 what it was. That the red variety absorbs more water than the blue is again 

 demonstrated. 



Erinoid is not nearly so absorbent as vulcanized fibre as shown by the 

 following results obtained for red erinoid and red fibre. In each sample the 

 total surface-area was about 135 sq. cms. 



The time of immersion was 65 hours for erinoid and 72 hours for fibre, 

 and the time of drying, exposed to air, 25 - 5 hours in each case. This drying 

 began at the same time in each case, and the samples were placed near each 

 other to ensure the same drying facilities. 



Allowing for the difference of the time of immersion the fibre probably 

 absorbed more than 2*5 times as much water as erinoid, while it was more 

 retentive of its absorbed water. 



In this test the erinoid was slightly swollen after immersion in water, but 

 not nearly so much so as the fibre, which increased in its thickness from 1 cm. 

 to 1*4 cm. 



The effect on the weight of erinoid by soaking it in different liquids for 

 two weeks has been investigated at the National Physical Laboratory and the 

 results obtained were these : — 



Liquid. 



Distilled water, 

 Sea water, 



Dilute sulphuric acid, 

 Mineral oil, 

 Castor oil, 



Percent, increase of weight. 



18-3 



19-0 



15-3 



Loss 0-02 



Loss 0-35 



3 h2 



