PAINTS AND VARNISHES 385 



in order to diminish the chances that the lead they may have 

 swallowed be dissolved by the free hydrochloric acid of the 

 gastric juice, as in some persons there is considerable secretion 

 of gastric juice in the empty stomach. 



Dust from the sandpapering of lead-painted surfaces is 

 one of the most important causes of lead poisoning. The 

 dust thus raised is inhaled and lodges on the mucous mem- 

 brane of the throat and nose and is then swallowed. In this 

 way the great bulk of such dust finds its way into the stom- 

 ach and not into the lungs. The workman is thus poisoned, 

 as the lead in the dust is dissolved by the free hydrochloric 

 acid in the gastric juice and is easily absorbed. This dust 

 is dangerous not only to the men doing the sandpapering, 

 but also to the others working nearby. The danger can 

 be entirely eliminated by the use of pumice-stone and water 

 in rubbing down coats. On a first coat, this process is apt 

 to raise the grain, and if the coat is on metal, it may cause 

 rust. In these cases the danger of poisoning can be elim- 

 inated by moistening the sandpaper with some cheap mineral 

 oil. Sandpaper so oiled lasts as well as when used dry, and 

 the results so far as the work is concerned are equally good. 



When metal surfaces are to be repainted they are usually 

 chipped and cleaned, the work often being done by a com- 

 pressed air machine. This method is very dangerous, and 

 a much better way, whether on wood or metal, is the burning 

 process already described. Though some authorities speak of 

 contracting lead poisoning by the use of the burning method, 

 their fears are not likely to be realized unless the painter 

 should hold the flame long in one place and thus cause con- 

 siderable smoke which might mechanically carry small 

 particles of lead. The boiling point of lead is so high that 

 the danger of evaporation is very slight, as comparatively 



