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When talking about the pH of salts, we're diving into whether a solution becomes acidic, neutral, or basic after dissolving the salt in water. Salts are made up of two parts: a cation, which is positive, and an anion, which is negative.
The nature of a salt's pH depends on the chemical properties of these ions:

• If both the cation and anion are strong, the solution is typically neutral.
• If the cation is strong and acts as a weak acid while the anion remains weak or basic, this often results in an acidic solution.
• Conversely, if the anion is strong and basic while the cation remains weak or neutral, the solution tends to be basic.

In the case of ammonium cyanate and anilinium cyanate, the balance between these ions' acidic and basic properties determines the pH of their solutions. Both the ammonium and anilinium cations are stronger acids than the cyanate anion's weak base, which tips the scale toward acidity in their solutions.

Ammonium cyanate is a compound that consists of an ammonium ion (\(NH_4^+\)) and a cyanate ion (\(OCN^-\)).
The ammonium ion comes from ammonia (\(NH_3\)), a weak base, and takes on the role of a weak acid. It can donate a proton in solution, thereby increasing acidity.
On the other hand, cyanate ions derive from isocyanic acid and are considered weak bases because they tend to accept protons less readily.
When combined into ammonium cyanate, the weak acidic power of \(NH_4^+\) slightly outweighs the weak base of \(OCN^-\). Thus, when ammonium cyanate dissolves in water, the resulting solution leans towards being acidic. This dominance by \(NH_4^+\) explains why the solution's pH is on the lower side of the scale, indicating acidity.

Anilinium cyanate is composed of anilinium ions (\(C_6H_5NH_3^+\)) and cyanate ions (\(OCN^-\)).
The anilinium ion is a result of protonating aniline (\(C_6H_5NH_2\)), which is a weak base, thus allowing the anilinium ion to act as a weak acid. It donates protons, increasing the hydrogen ion concentration in a solution.
Meanwhile, the cyanate ion (\(OCN^-\)), similar to in ammonium cyanate, is not a strong base and accepts protons reluctantly.
In the context of anilinium cyanate, the acidic property of the anilinium ion distinctly surpasses the weak basic property of the cyanate ion. Hence, the solution becomes acidic when anilinium cyanate is dissolved in water.
This clear acidic influence from the anilinium ion makes the pH of the solution lower, further supporting the acidic behavior observed.