4 o + TEE POPULAR SCIENCE MONTHLY 



seemed to offer the most resistance to washing with soap and water. 

 Thus, when the material had been thoroughly saturated with a solution 

 made up of sodium tungstate, zinc sulphate and enough acetic acid to 

 prevent the precipitation of the zinc tungstate, and the goods after 

 drying were thoroughly steamed, the fireproofing was certainly fixed 

 to some extent, since it required several washings before the material 

 burnt at all freely. But no amount of variation of the conditions 

 produced a really good result and this combination had therefore to 

 be abandoned. Since the tungstate proved to be unsuitable to the 

 exacting conditions of the problem, a general examination of almost 

 every variety of salt, including ferrocyanides, aluminates, arseniates, 

 antimoniates, zincates and plumbates was made. Many of these could 

 not be employed in connection with wearing apparel in any case because 

 of their poisonous nature, but it was thought that this general exam- 

 ination, which lasted several months, might yield some indication of 

 the type of salt likely to prove resistant to soap and water, if, indeed, 

 such type of salt existed at all. And as a matter of fact these experi- 

 ments did prove to be most valuable, because when the results were all 

 tabulated, the generalization gradually became apparent that certain 

 soluble salts such as aluminates, antimoniates, zincates and plumbates, 

 in which the oxide of the metal functions as an acid, yielded precipi- 

 tates, especially with zinc and tin salts which exhibited much greater 

 resistance to washing than the commoner insoluble salts, such as 

 barium sulphate or magnesium phosphate. This generalization ulti- 

 mately led to a very careful examination of the salts of tin, because, as 

 is well known, the oxides of tin dissolve in alkalis to form stannites 

 and stannates and tin therefore belongs to the class of salts just men- 

 tioned and it very soon became evident that these salts do actually 

 possess the power of combining with the fiber to a greater extent than 

 any of the salts which had previously been experimented with. 



In one experiment it was noted that a piece of flannelette, which 

 had first been saturated with a solution of sodium stannate and dried, 

 and afterwards similarly treated with a solution of zinc chloride, was 

 quite non-inflammable. After the sample had been subjected to a 

 vigorous washing with soap and water a considerable amount of the 

 fireproofing still remained, because, when a light was applied to the 

 cloth, it only ignited with difficulty, burned very slowly, and either 

 went out of itself or was easily extinguished on shaking the material. 



This development was so promising that the experiment was 

 repeated in a great variety of ways, but, although several results were 

 obtained which were much better than anything which had been seen 

 before, it was disappointing to find that in all the cases the greater 

 part of the fireproofing was lost after repeated washings. 



In a later series of experiments the first solution was again sodium 



