Very short, a chemical tanker is like an oil tanker but with more and smaller tanks. Some vessel f.ex. Stolt Nielsen K40-class have up to 56 tanks. The tanks are special equipped to handle many types of cargo. Here are some examples of the stuff they carry and the problems they face:

Vodka. In order to ship this in a sober manner, the tanks must be perfectly clean. The tanks have highly efficient washing machines to make this possible. Highly skilled (and cheerful?) surveyors are actual tasting the product during loading and discharging to ensure the customer is not left with a bad taste in their mouth.

Vinyl Acetate is used for making plastics. Unfortunately this stuff have a tendency to make plastic on it's own when you least expect it. This is called polymerisation and you can probably imagine what it would look like if these things get out of hands! To avoid any mishaps another chemical is mixed into the tank to slow down this process, the so-called inhibitor.

TolueneDiIsocyanate is a.o. used to make your bed-mattress porous and thus nice and comfortable. TDI reacts violently when exposed to air. In order to avoid anything crazy from happening (explosions etc.) the tanks are filled with nitrogen gas before loading to get rid of the air inside. Still wonder why these mattresses are so expensive?

Acetic Anhydride is very popular with the security-police in regime ruled countries. It makes tear gas. To avoid the same fate as many couragious civic rights fighters, the crew must wear masks or "diving gear" when handling this product. Fortunately most of this stuff are used for the common good.

Soya Oil, what would french fries be without it? This is shipped in large quantity on tankers. It freezes very easily so the tankers are equipped with heating coils keeping the oil on a temperature of 40-60 deg C.

Rubber. Did you know that rubber is liquid and transported on tankers before turned into tyres etc.? Now you know!

Acrylates have a pleasant smell but only if you have only one drop of it. On the other hand, filling 2.000.000 litres of it into a tanker soon makes your nose start begging for mercy! It is common to turn of the air condition system on tanker vessels when handling this grade. This saves the ship from smelling (...) later. Acrylates are used for toilet articles, perfumes, foodstuff etc.

Propylene Oxide is sometimes added into Jet Fuel to get a better burn. So when loading this into a tank just remember that smoking is strictly prohibited and, believe me, dangerous for your health.

Drinking water was transported to the troops in the Gulf war by a chemical tanker.

The largest chemical shipping companies in the world:

Stolt-Nielsen Parcel Tankers, New York, USA

Odfjell Tankers KS, Bergen, Norway

J.O. Tankers, Rotterdam, Holland