CHAPTER VIII. 



SALINE AND ARTIFICIAL SEA WATER SOLUTIONS 



SALINES AND SEA- WATERS: GENERAL 



Artificial salt solutions have been prepared which attempt to dupli- 

 cate both the osmotic and ionic properties of the internal or external 

 environments of given organisms. The aquatic media in which animals live 

 are replaced by artificial sea-waters, while the Ringer's and associated 

 solutions are substitutes for the tissue fluids (and/or plasma) of the 

 various species. In many cases, it suffices to use a solution of a single 

 compound which has the same osmotic pressure as the medium, a so-called 

 isotonic solution. Such solutions, though osmotically normal, are phys- 

 iologically imperfect due to ionic imbalance. 



The chief components of these artificial salines are sodium, potas- 

 sium, calcium, and magnesium cations, and the anions chloride sulfate, 

 and bicarbonate. They are readily added in the form of six salts mixed 

 in the proper proportions, and at the proper total concentration. Reagent 

 Grade Merck chemicals and distilled water should be used in all cases. 

 Merck's special reagent for biological use sodium chloride should be used 

 to avoid toxic impurities sometimes found in other brands. The bicar- 

 bonate must not be added until the solution is almost diluted to volume, 

 nor before heat sterilization (if necessary) or the calcium will precip- 

 itate. 



SALT STANDARDS: 



For convenience in making up the artificial sea-waters and phys- 

 iological salt solutions, 8 liter stock bottles of LOOM solutions of 

 the major components are kept above the Chemist's work bench. These 

 are connected to self-filling burettes for ready delivery of the proper 

 volumes of the standard salt solutions. 



Sodium chloride, potassium chloride, sodium bicarbonate, and mag- 

 nesium sulfate are not hygroscopic, and their solutions may be prepared 

 by weighing out the proper amount of the salt as it comes in the bottle, 

 and dissolving to volume. Calcium chloride and magnesium chloride are 

 too hygroscopic for this procedure, and therefore approximate amounts 

 of these salts are dissolved to volume and the resulting solutions stand- 

 ardized and adjusted to LOOM. 



The standardization is done by determining the chloride content, 



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