= Sulfur-35
{title2=$^{35}\mathrm S$}
<Sulfur-35> is a radioactive <isotope> of <sulfur> with 16 <protons> and 19 <neutrons>. It undergoes <beta-minus decay> to stable <chlorine-35>. The cited evaluation gives a <half-life> of $87.25(15)\,\mathrm d$, much longer than the roughly 14-day <half-life> of <phosphorus-32>.<Sulfur-35 in LNE-LNHB Table de Radionucleides>[Page1, decay scheme and nuclear data; February2012 evaluation]{ref}
The 1952 <Hershey-Chase experiment> used <sulfur-35> to follow the sulfur-containing <protein> component of <Bacteriophage T2>. Agitation released about 75 percent of the phage sulfur label, compared with about 15 percent of the phosphorus label, while the infected cells could still yield progeny. The complementary labels helped separate the fates of external protein and entering <DNA>.<Independent functions of viral protein and nucleic acid in growth of bacteriophage by A. D. Hershey and Martha Chase>[Abstract, points4–6]{ref} A label identifies the material carrying it under the specified labelling scheme; detection alone does not establish the function of every component.
Using the quoted <half-life>, a closed sample observed 14 days later retains $2^{-14/87.25}\approx0.895$ of its starting <radioactivity>. That is about 90 percent, rather than one half. Comparing sulfur-35 and phosphorus-32 signals over days therefore requires isotope-specific decay accounting. Detector efficiency and recovery of labelled material also belong to the measurement model; equal raw counts do not automatically mean equal numbers of labelled atoms.
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