Complex sentence: The helmet was a flannel bag, soaked in glycerine, hyposulphite and sodium bicarbonate and known as a Smoke helmet and by 6 July all of the British troops in France had received one.
Split into simpler sentences: The helmet was a flannel bag, soaked in glycerine, hyposulphite and sodium bicarbonate and known as a Smoke helmet. By 6 July, all British troops in France had received one.