Licence: Public Domain Mark
Credit: Physiological histology, methods and theory / by Gustav Mann. Source: Wellcome Collection.
40/524 page 18
Licence: Public Domain Mark
Credit: Physiological histology, methods and theory / by Gustav Mann. Source: Wellcome Collection.
![ion OH', there being formed electrically inactive, neutral water. In this particular case the two remaining radicals, namely sodium and chlorine, remain as electrical ions in solution : (IT + CIO + (Na* + OHO - (H* + OHO + Na* + Cl' - H20 + Ha* + Cl'. To measure the amount of acid or base present in a solution means to determine the number of hydrogen or hydroxyl ions. For this purpose ‘ normal ’ solutions are employed. A 1 normal ’ solution is prepared by dissolving the gram molecular weight or ‘mol’ of any monovalent substance in 1,000 cc. or i litre of water. A normal caustic soda solution is therefore obtained by dissolving Na-f O-f H = 23 05+ 16+ i-oi or 40-06 grms. in 1,000 cc. of water. Similarly a normal hydrochloric acid solution con¬ tains 36-46 grms. of HC1 (Cl = 35-45 and H = i-oi). As a litre of normal caustic soda solution contains 17-01 grms. of the basic hydroxyl group OH', and as a litre of normal hydrochloric acid con¬ tains i-oi grm. of the acid hydrogen ion H*, it follows that by the union of 17-01 grms. of OH and the i-oi grm. of hydrogen the sub¬ stance water, H20 with a gram molecular weight of [i-oi 4- i-oi 4- 16] or 18 02, will be formed. As water is a neutral compound we know that neutralization must mean the union of the basic OH' with the acid H\ To neutralize means to form water. If 1,000 cc. of normal soda solution neutralize 1,000 cc. of normal hydrochloric acid solution, it follows that 1 cc. of NaOH will also neutralize 1 cc. of HC1, however much they may be diluted with water. This fact is made use of for preparing deci- and centi- normal acid and basic solutions by diluting the normal solution 10 or 100 times. In histology normal solutions diluted 1,000 and even 10,000 times have still very marked effects, and are required for determining the relative acid and basic affinities between dyes and tissue constituents. The estimation of acidity or basicity by means of neutralization experiments is called titration. Salts. The ions of an electrolyte as regards their electro-affinities may be both strong, both weak, or one of the radicals may be feeble while the other is strong. Thus in sodium chloride the an-ion Cl' and the kat-ion Na’ are both strong ; in mercuric cyanide the an-ion CN' and the kat-ion Hg* are both feeble ; in corrosive sublimate the an-ion Cl' is strong while the kat-ion Hg* is feeble ; and in sodium carbonate the an-ion CO/ is feeble while the kat-ion Na' is strong \ When the salts just mentioned dissolve in water, no action on or by the latter will take place if the an-ion and kat-ion radicals are both equally strong, as in sodium chloride. It is different, however, with such ill-matched radicals as are met with in corrosive sublimate or sodium carbonate, as is explained later. 1 Compare the table of electro-affinities on p. 14.](https://iiif.wellcomecollection.org/image/b31356096_0040.jp2/full/800%2C/0/default.jpg)
