The synonym for water gas when used in the production of methanol is :

Explanation

To solve the question about the synonym for water gas when used in the production of methanol, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Water Gas**: Water gas is a mixture primarily composed of carbon monoxide (CO) and hydrogen (H2). It is produced through the reaction of steam with carbon (usually in the form of coke) at high temperatures.

2. **Identify the Production Process**: The production of water gas involves passing steam over red-hot carbon. This reaction is endothermic, meaning it requires heat to proceed. The chemical reaction can be represented as:
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