| 摘要 |
<p>The invention comprises aqueous solutions of the salts of bis- or tris-(b -sulphato-alkyl)-sulphonium inner salts of the formula:- <FORM:1032882/C2/1> wherein R1, R2, R3 and R4 are H or C1-C3 alkyl; R5 is the group (CHR3-CHR4-OSO3H) or a straight or branched substituted or unsubstituted alkyl, or a substituted or unsubstituted alkenyl, aryl, aralkyl, alicyclic or heterocyclic group containing a buffer system adapted to maintain the pH of the solution within the range 2.0 to 3.5, preferably in the range 2.7 to 3.3. The said solutions are stated to result in an improvement in the chemical stability of the salts of the sulphonium inner salts and may be obtained by adding to aqueous solutions of the salts a weak acid or an ammonium, alkali or alkaline earth metal salt of a weak acid and adjusting the pH to a desired value. Weak acids which are used are monobasic acids with a pK value not less than 2.0 nor greater than 5.0, for instance formic acid (pK 3.7) and acetic acid (pK 4.7) and polybasic acids with a pK value for the first hydrogen not less than 2.0 nor greater than 5.0, for example phosphoric acid (pK 2.15), citric acid (pK 3.1), tartaric acid (pK 3.0), succinic acid (pK 4.0) and maleic acid (pK 2.9). The amount of the weak acid or salt of a weak acid added to the aqueous solution is a small percentage of the weight of the solution preferably from 0.25% to 5%.</p> |
