Shackleton (1967) investigated the attainment of isotopic equilibrium between ocean water and the benthonic foraminifera genus Uvigerina, focusing on isotopic changes in the ocean during the last glacial period. He showed that even when using non-standard analytical methods, foraminiferal test oxygen isotopic compositions can be expressed in terms of the PDB standard. By comparing with an empirical relationship for molluscs and inorganic calcite precipitation, it was found that Uvigerina deposits its test at or near isotopic equilibrium in the temperature range of 0.8°C to 7°C. The isotopic composition of tests from the last glacial period indicates a significant change in the mean oxygen isotopic composition of the oceans, exceeding 1% for about 20,000 years and 0.5% for about 70,000 years. The oxygen isotope method for determining paleotemperatures is widely used to study past climate changes. Urey's idea was later developed by Epstein et al., and most researchers use methods based on their work. Shackleton describes significant changes in technique and interpretation necessary for accurate oxygen isotope analysis. The procedure for oxygen isotope analysis of carbonate involves three stages: cleaning the sample, extracting carbon dioxide for mass spectrometric analysis, and comparing the isotopic composition of the gas with a laboratory standard. Various methods have been used to extract carbon dioxide, with some involving heating in helium or vacuum. The precision of these methods has improved, allowing for standard deviations of about 0.1‰. Fritz and Fontes found that grain size affects the isotopic composition of evolved carbon dioxide, leading to potential errors in paleotemperature estimates. Shackleton's experiments showed that grain size does not significantly affect the isotopic composition when using a high-precision mass spectrometer. He also investigated the effects of acid strength, sample quantity, and roasting, finding that the experimental system allows for an analytical precision of ±0.1%o. The relationship used to derive paleotemperatures from oxygen isotope determinations was based on a belemnite standard from the Cretaceous Pee Dee formation. PDB is considered a carbonate standard, but it is also used as a carbon dioxide standard. Shackleton argues that the equation derived from PDB is only valid for carbonates with the same grain-size distribution as those analyzed in the original study. However, his method allows for comparisons regardless of grain size, provided a carbonate comparison standard is used. Shackleton also discusses the purification pretreatment of samples, noting that the method of sample pretreatment can affect oxygen isotope analyses. He reanalyzed samples from core Al79-4 using vacuum roasting and found results similar to those obtained by Emiliani in Chicago. He concludes that the procedure described allows for the expression of the oxygen isotopic composition of foraminifera inShackleton (1967) investigated the attainment of isotopic equilibrium between ocean water and the benthonic foraminifera genus Uvigerina, focusing on isotopic changes in the ocean during the last glacial period. He showed that even when using non-standard analytical methods, foraminiferal test oxygen isotopic compositions can be expressed in terms of the PDB standard. By comparing with an empirical relationship for molluscs and inorganic calcite precipitation, it was found that Uvigerina deposits its test at or near isotopic equilibrium in the temperature range of 0.8°C to 7°C. The isotopic composition of tests from the last glacial period indicates a significant change in the mean oxygen isotopic composition of the oceans, exceeding 1% for about 20,000 years and 0.5% for about 70,000 years. The oxygen isotope method for determining paleotemperatures is widely used to study past climate changes. Urey's idea was later developed by Epstein et al., and most researchers use methods based on their work. Shackleton describes significant changes in technique and interpretation necessary for accurate oxygen isotope analysis. The procedure for oxygen isotope analysis of carbonate involves three stages: cleaning the sample, extracting carbon dioxide for mass spectrometric analysis, and comparing the isotopic composition of the gas with a laboratory standard. Various methods have been used to extract carbon dioxide, with some involving heating in helium or vacuum. The precision of these methods has improved, allowing for standard deviations of about 0.1‰. Fritz and Fontes found that grain size affects the isotopic composition of evolved carbon dioxide, leading to potential errors in paleotemperature estimates. Shackleton's experiments showed that grain size does not significantly affect the isotopic composition when using a high-precision mass spectrometer. He also investigated the effects of acid strength, sample quantity, and roasting, finding that the experimental system allows for an analytical precision of ±0.1%o. The relationship used to derive paleotemperatures from oxygen isotope determinations was based on a belemnite standard from the Cretaceous Pee Dee formation. PDB is considered a carbonate standard, but it is also used as a carbon dioxide standard. Shackleton argues that the equation derived from PDB is only valid for carbonates with the same grain-size distribution as those analyzed in the original study. However, his method allows for comparisons regardless of grain size, provided a carbonate comparison standard is used. Shackleton also discusses the purification pretreatment of samples, noting that the method of sample pretreatment can affect oxygen isotope analyses. He reanalyzed samples from core Al79-4 using vacuum roasting and found results similar to those obtained by Emiliani in Chicago. He concludes that the procedure described allows for the expression of the oxygen isotopic composition of foraminifera in