The fissure in the foundation wall where the Old Ferry warehouse joined the museum basement was three inches wide, weeping a nonstop, sluggish trickle of gray lime slurry that hissed as it touched the wet river brick floor. Imran Bell pulled his breathing mask over his face, clicked the breath out valve clear with a sharp snort. Then it knelt on the cold red bricks.
He drew forth a long pair of brass metal tongs and gripped a two-inch strip of the blue cabbage indicator paper. He leaned forward until the black rubber rim of his mask was within six inches of the crack. He thrust the paper directly into the plume of hot vapor escaping from the stonework.
The transformation was instant. The pale blue vegetable dye didn’t fade or slowly shift toward violet. It flashed into a violent, blood-red crimson before the paper was even fully pushed in into the fissure. The acidic vapor was so packed that the edges of the paper began to curl and dissolve in the humid draft.
‘pH two point eight,’ Imran muttered through his speaking chest muscle, his voice sounding hollow and metal. ‘Rotten-egg acid vapor mixed with white-hot stone steam. It’s like leaning over an open vat of battery burning acid.’
