SODIUM. 39 



ACTION AND USES. 

 1. IMMEDIATE LOCAL ACTION AND USES. 



Externally, soda possesses an action similar to that of 

 potash, but is much less frequently used as a caustic. Solutions 

 of the carbonates may be employed to neutralise caustic acids ; 

 in eczema and itching disorders of the skin ; and in extensive 

 burns. Soda compounds with olive oil constitute hard soap. 



Internally, Soda closely resembles potash in its action on 

 the alimentary canal, but is more powerful because much less 

 diffusible, i.e. more slowly absorbed. It is antacid to the 

 contents of the stomach, relieving acidity due to indigestion, in 

 the form either of the bicarbonates, soda-water, the officinal 

 lozenges, or as a mixture with sal- volatile and an essential oil, 

 such as peppermint, given after meals. As a stomachic, stimu- 

 lating the flow of the gastric juice, bicarbonate of soda is more 

 commonly given than the other alkalies, in doses of gr. 8 to 

 gr. 15, shortly before meals. Part of the salt at the same time 

 becomes converted into the chloride, which assists the digestion 

 of albumen. The alkali also liquefies tenacious mucus, and 

 thus prevents decomposition, the juice reaching the food more 

 freely. Common salt is a safe and available emetic. 



The salts of soda, being much less diffusible than those of 

 potash, pass on into the small intestine. Here the sulphate and 

 phosphate of soda and tartarated soda (Rochelle salt) act as 

 saline purgatives. The sulphate, which is a constituent of 

 several natural purgative waters, including Carlsbad, Friedrichs- 

 hall, Hunyadi Janos, and Bilin, is the most powerful of these, 

 producing an abundant watery evacuation. It is used as a hydra- 

 gogue in dropsies, especially in ascites from liver disease, in 

 congestion of the portal system, and as a habitual purgative. 

 The phosphate is a milder, but sufficiently active, purgative, less 

 unpleasant to the palate ; it is often given to children. Soda 

 tartarata, the purgative basis of the Seidlitz powder, is familiar 

 as a milder intestinal stimulant, of use in completing the effect 

 of purgative pills. The chloride is an anthelmintic. 



2. ACTION ON THE BLOOD AND ITS USES. 



The salts of soda are slowly absorbed into the blood, and 

 slowly excreted from it, remaining in it chiefly as the bicar- 

 bonate and phosphate. Taken, as they constantly an', in food, 

 these salts are the chief sources of the natural alkalinity of the 

 liquor sanguinis, which may be increased "by their medicinal 

 exhibition as well as by the tartratc, Ilochelle salt, and even 

 the sulphate. This effect of soda as an alkaliniser of the 



