Soft Boiled Egg Science
As an answer to your first question:  what chemicals do the white and yolk contain?

Unlike the yolk, which is high in lipids (fats), egg white contains almost no fat, and carbohydrate content is less than 1%, it contains water, protein, trace minerals, fatty material, vitamins, and glucose. wikipedia

To get this kind of soft eggs: 


Whites set at 155°F (68°C) and yolks set at 158°F (70°C). For best results, heat water to 180°F (82°C) as measured on an instant-read thermometer. After adding eggs, adjust heat to maintain temperature at 180°F for about 6 mins (+/- 15 seconds). If you do not have a thermometer, keep the water at the early simmer stage when tiny bubbles are just beginning to break the surface. food-lab-science-of-how-to-cook-perfect-boiled-eggs

So I guess what you have read is true. Hope to enjoy.