@cire You link says they start at a pH between five and six, invert at pH=1.6 and then "neutralise it". No specifics given there. But I did learn that Ragus is 'sugar' spelled backwards. Never noticed.
Also thanks for your recipe, sounds properly systematic. I observed the same effects when I did my sugars.
Sorry, yes, your observation is correct, but when seeing pH 5, I assumed it was the original text, but is not.
Can I suggest that should you neutralize your invert to pH 7 or higher, limit its shelf life to less than Ragus suggest and recognize the potential impact on copper finings effectiveness if added in large quantity to a boil.
How did this particular invert sugar contribute to the deaths of the heavy drinkers?
The sulfuric acid used for inversion contained arsenic and the residue got into the beer. Several of the deaths were traced back to drinking beer from one particular brewery.
It's getting very difficult to find much accurate history of Britain's activities, past and present in current internet offerings, but maybe that is true of other places too. However, there is a wiki page on this matter with potentially more inaccuracies than truths.
https://en.wikipedia.org/wiki/1900_English_beer_poisoning
A worker at the same sugar works who stirred the sugar syrup from a platform above the boiler, fell into the vessel on another occasion.
Beer was blamed for many problems in the civilized world during this period. Not just the temperance movement put the cause to excessive drinking, the law might also approve such a cause to resolve an otherwise uncomfortable problem.