Here’s a short fragment of Accident by Agatha Christie.
Evans paid no attention, but went on. ‘You interrupted me just now. After Marsh’s test, Merrowdene heated a substance in a test tube, the metallic residue he dissolved in water and then precipitated it by adding silver nitrate. That was a test for chlorates. A neat, unassuming little test. But I chanced to read these words in a book that stood open on the table. “H2SO4 decomposes chlorates with evolution of Cl2O4. If heated, violent explosions occur, the mixture ought therefore to be kept cool and only very small quantities used.”’What book was that? Googling gave me The Elements of Chemical Arithmetic with a Short System of Elementary Qualitative Analysis by J. Milnor Coit, Ph.D., published in 1886. On page 80, section 103, I’ve found the original description (shortened in Agatha Christie’s version):
H2SO4 decomposes chlorates with evolution of Cl2O4, a greenish-yellow gas having a powerful odor. If heated, violent explosions occur; the mixture ought therefore to be kept cold, and only very small quantities should be used.The full text of this, apparently, still very useful book is copyright-free.