I need to increase my pancake recipe 4.5 times. I seem to remember that the salt and soda are increased at a smaller ratio than the rest of the ingredients. Is that true, and what is the correct ratio for salt and baking soda?
In a pancake recipe, it is unlikely to be a practical concern.
The reason these ideas get started is because:
Pancakes, in particular are very forgiving and flexible. They should scale linearly, in practice.
If you are exceptionally concerned, you can find a commercial recipe (often called a formula) which is expressed by weight and is much more accurate. These should scale quite effectively.
One issue you may have is how long it takes to cook the larger batch of pancakes, and that you will be losing leavening from the batter during that time. Unless you have four people working four griddles, you may be better off just making a large batch of dry pancake mix (everything except, typically, fat, eggs, water, and dairy depending). You can then mix in the liquids in smaller amounts as you go along, essentially continually creating fresh batter for yourself.