The analytical methods committee of the Royal Society of Chemistry reported the following results on the levels of tin recovered from samples of blended fish–meat product after boiling with hydrochloric acid for 30, 45, 60, and 70 minutes, respectively

(Source: The Determination of Tin in Organic Matter by Atomic Absorption Spectrometry, The Analyst (1983), vol. 108, pp. 109-115,  VII. Used with permission.) During the experiment the authors noted “that maintaining boiling for 70 minutes without sputtering and enforced cooling was difficult. The effect is shown in a lower mean recovery and much greater variability of results.” Write a brief report justifying these conclusions.